From 356e6cefe04d6919cc948e462464d392052c224d Mon Sep 17 00:00:00 2001
From: Adrien Alberti <adrien@aalberti.com>
Date: Thu, 22 Oct 2026 11:52:49 +0200
Subject: [PATCH 1/2] M12: type or pick an architect's 1:N drawing scale in the
 Measure panel, applied at once

On top of #3011's page unit, the Drawing scale block gets a "1:N" field (1:50,
1/100, 50, 1:2,5 are read; zero, negative, huge and malformed values are
refused with a message) and a combo of common architect scales (1:1 to
1:1000). Either one fills the existing fields (1 mm of paper = N mm, shown in
metres) and applies the scale to the page without a second click, only when
the document allows annotation. Apply scale is unchanged.
---
 crates/ui-egui/src/measure_ui.rs | 142 ++++++++++++++++++++++++++++++-
 crates/ui-egui/tests/control.rs  |  52 +++++++++++
 parity/acrobat-features.toml     |   2 +-
 3 files changed, 193 insertions(+), 3 deletions(-)

diff --git a/crates/ui-egui/src/measure_ui.rs b/crates/ui-egui/src/measure_ui.rs
index f91e4bf3f..d80ecca3e 100644
--- a/crates/ui-egui/src/measure_ui.rs
+++ b/crates/ui-egui/src/measure_ui.rs
@@ -55,6 +55,10 @@ pub struct MeasureView {
     pub unit: String,
     /// The unit picked for the page side of the scale; `None` follows `unit`.
     pub page_unit: Option<PageUnit>,
+    /// The "1:N" field of the drawing scale, as typed.
+    pub ratio_text: String,
+    /// The "1:N" field was edited and not yet applied.
+    ratio_dirty: bool,
     pub precision: u8,
     pub name: String,
     pub whole_page: bool,
@@ -83,6 +87,8 @@ impl Default for MeasureView {
             real_distance: 1.0,
             unit: "in".into(),
             page_unit: None,
+            ratio_text: String::new(),
+            ratio_dirty: false,
             precision: 2,
             name: "Drawing scale".into(),
             whole_page: true,
@@ -99,6 +105,35 @@ impl Default for MeasureView {
 pub(crate) fn page_unit_of(picked: Option<PageUnit>, unit: &str, display: crate::units::Unit) -> PageUnit {
     picked.or_else(|| PageUnit::from_label(unit)).or_else(|| PageUnit::from_label(display.label())).unwrap_or(PageUnit::Pt)
 }
+/// Drawing scales an architect's rule offers, as the N of 1:N.
+pub(crate) const RATIOS: [f64; 10] = [1.0, 5.0, 10.0, 20.0, 25.0, 50.0, 100.0, 200.0, 500.0, 1000.0];
+/// "1:200", "1/200", "1 : 200" or a bare "200" (a comma works as the decimal mark), as the N of 1:N.
+/// `None` for anything else, for zero, negative or absurd values.
+pub(crate) fn parse_ratio(text: &str) -> Option<f64> {
+    let text = text.trim().replace(',', ".");
+    let n = match text.split_once([':', '/']) {
+        Some((one, n)) => n.trim().parse::<f64>().ok()? / one.trim().parse::<f64>().ok()?,
+        None => text.parse::<f64>().ok()?,
+    };
+    (n.is_finite() && (1e-6..=1e9).contains(&n)).then_some(n)
+}
+/// "1:200", or "1:2.5" for a ratio that isn't a whole number.
+pub(crate) fn format_ratio(n: f64) -> String {
+    let rounded = (n * 100.0).round() / 100.0;
+    if (rounded - rounded.round()).abs() < 1e-9 { format!("1:{}", rounded.round()) } else { format!("1:{rounded}") }
+}
+/// Fill the scale fields for 1:N: 1 mm on the page is N mm, shown in metres. Returns `false`, changing nothing, when `n` is not a usable ratio.
+pub(crate) fn set_ratio(state: &mut MeasureView, n: f64) -> bool {
+    if !n.is_finite() || n <= 0.0 {
+        return false;
+    }
+    state.unit = "m".into();
+    state.page_unit = Some(PageUnit::Mm);
+    state.drawing_points = 1.0;
+    state.real_distance = n / 1000.0;
+    state.ratio_text = format_ratio(n);
+    true
+}
 impl MeasureView {
     pub fn cancel(&mut self) {
         self.points.clear();
@@ -363,7 +398,27 @@ fn panel_body(app: &mut PdfCraftApp, ui: &mut egui::Ui, _t: &Tokens) {
         ui.add(egui::Slider::new(&mut state.sensitivity, 1.0..=20.0).text(tl!("Sensitivity")));
     }
     ui.separator();
-    ui.label(tl!("Drawing scale"));
+    // "1:N" fills the fields below and applies at once, as does picking a common scale.
+    let mut chosen = None;
+    ui.horizontal(|ui| {
+        ui.label(tl!("Drawing scale"));
+        let typed = ui.add(crate::widgets::line(&mut state.ratio_text).hint_text("1:100").desired_width(56.0).char_limit(16));
+        typed.widget_info(|| egui::WidgetInfo::labeled(egui::WidgetType::TextEdit, true, tl!("Scale")));
+        state.ratio_dirty |= typed.changed();
+        if typed.lost_focus() && std::mem::take(&mut state.ratio_dirty) {
+            match parse_ratio(&state.ratio_text) {
+                Some(n) => chosen = Some(n),
+                None => state.error = Some(tl!("Enter a scale such as 1:50.").into()),
+            }
+        }
+        egui::ComboBox::from_id_salt("measure-common-scales").selected_text(tl!("Common scales")).width(20.0).show_ui(ui, |ui| {
+            for n in RATIOS {
+                if ui.selectable_label(state.ratio_text == format_ratio(n), format_ratio(n)).clicked() {
+                    chosen = Some(n);
+                }
+            }
+        });
+    });
     ui.horizontal(|ui| {
         ui.add(egui::DragValue::new(&mut state.drawing_points).range(0.000001..=1e9));
         let page_unit = page_unit_of(state.page_unit, &state.unit, units);
@@ -427,7 +482,16 @@ fn panel_body(app: &mut PdfCraftApp, ui: &mut egui::Ui, _t: &Tokens) {
         }
     }
     let export = ui.button(tl!("Export measurements as CSV")).clicked();
-    if apply && let Some(info) = info {
+    if let Some(n) = chosen
+        && set_ratio(state, n)
+    {
+        state.error = None;
+    }
+    // Apply scale, or a 1:N typed or picked: the fields are applied to the document at once.
+    if (apply || chosen.is_some())
+        && doc.allows_annotation()
+        && let Some(info) = info
+    {
         let result =
             doc.measurement_to_user(page, [0.0, 0.0]).and_then(|a| doc.measurement_to_user(page, [1.0, 0.0]).map(|b| (a, b))).and_then(|(a, b)| {
                 let page_unit = page_unit_of(state.page_unit, &state.unit, units);
@@ -513,3 +577,77 @@ fn export_csv(app: &mut PdfCraftApp) {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    /// What Apply scale builds from the panel's fields, then a distance read with it.
+    fn measured(state: &MeasureView, from: Point, to: Point) -> f64 {
+        let page_unit = page_unit_of(state.page_unit, &state.unit, crate::units::Unit::Points);
+        let scale = Scale::ratio([0.0, 0.0], [1.0, 0.0], state.drawing_points, page_unit, state.real_distance, &state.unit, 4).expect("scale");
+        measure::reading(Kind::Distance, &[from, to], &scale).expect("reading").value
+    }
+
+    #[test]
+    fn typed_ratios_are_read_leniently() {
+        assert_eq!(parse_ratio("1:200"), Some(200.0));
+        assert_eq!(parse_ratio(" 1 : 50 "), Some(50.0));
+        assert_eq!(parse_ratio("1/20"), Some(20.0));
+        assert_eq!(parse_ratio("250"), Some(250.0));
+        assert_eq!(parse_ratio("1:2,5"), Some(2.5));
+        assert_eq!(parse_ratio("2:1"), Some(0.5));
+    }
+
+    #[test]
+    fn invalid_ratios_are_refused() {
+        for bad in ["", " ", ":", "1:", ":50", "1:0", "0", "-5", "1:-5", "0:5", "abc", "1:abc", "1:50:2", "1:inf", "NaN", "1e12", "1:1e12"] {
+            assert_eq!(parse_ratio(bad), None, "{bad:?}");
+        }
+    }
+
+    #[test]
+    fn ratios_are_written_as_people_say_them() {
+        assert_eq!(format_ratio(50.0), "1:50");
+        assert_eq!(format_ratio(2.5), "1:2.5");
+        assert_eq!(format_ratio(0.5), "1:0.5");
+        for n in RATIOS {
+            assert_eq!(parse_ratio(&format_ratio(n)), Some(n));
+        }
+    }
+
+    #[test]
+    fn every_offered_ratio_reads_paper_length_times_n_in_metres_whatever_the_unit_was() {
+        for unit in ["mm", "cm", "m", "km", "in", "ft"] {
+            for n in RATIOS {
+                let mut state = MeasureView { unit: unit.into(), ..Default::default() };
+                assert!(set_ratio(&mut state, n));
+                assert_eq!(state.unit, "m");
+                // 72 pt is one inch of paper: 25.4 mm x N, shown in metres.
+                let v = measured(&state, [0.0, 0.0], [0.0, 72.0]);
+                let expected = 25.4 * n / 1000.0;
+                assert!((v - expected).abs() < 1e-9 * expected.max(1.0), "1:{n} in {unit} gave {v}, wanted {expected}");
+            }
+        }
+    }
+
+    #[test]
+    fn any_starting_unit_becomes_metres() {
+        let mut state = MeasureView { unit: "yards?".into(), ..Default::default() };
+        assert!(set_ratio(&mut state, 50.0));
+        assert_eq!(state.unit, "m");
+        // 1 mm of paper at 1:50 is 50 mm.
+        let v = measured(&state, [0.0, 0.0], [72.0 / 25.4, 0.0]);
+        assert!((v - 0.05).abs() < 1e-9, "{v}");
+    }
+
+    #[test]
+    fn an_unusable_ratio_changes_nothing() {
+        let mut state = MeasureView::default();
+        let before = (state.drawing_points, state.real_distance, state.unit.clone(), state.page_unit);
+        for n in [0.0, -1.0, f64::NAN, f64::INFINITY] {
+            assert!(!set_ratio(&mut state, n));
+        }
+        assert_eq!((state.drawing_points, state.real_distance, state.unit.clone(), state.page_unit), before);
+    }
+}
diff --git a/crates/ui-egui/tests/control.rs b/crates/ui-egui/tests/control.rs
index 9082c689c..516d85ed6 100644
--- a/crates/ui-egui/tests/control.rs
+++ b/crates/ui-egui/tests/control.rs
@@ -1362,6 +1362,58 @@ fn a_1_to_50_scale_in_millimetres_measures_a_10_mm_line_as_500_mm() {
     assert_eq!(measurements[0].reading.unit, "mm");
 }
 
+#[test]
+fn a_plan_scale_picked_or_typed_applies_at_once() {
+    use pdfcraft_engine::measure::{self, Kind};
+    let (mut h, c) = harness_pages(1);
+    let doc = h.state().views[0].id;
+    ok(&mut h, &c, "ui.command", json!({"id":"measure.scale"}));
+    h.run_steps(3);
+    h.state_mut().views[0].measure.unit = "m".into();
+    h.run_steps(2);
+    // 60 mm of paper.
+    let line = [[20.0, 20.0], [20.0 + 60.0 / 25.4 * 72.0, 20.0]];
+    let read = |h: &Harness<'static, PdfCraftApp>| {
+        let scale = h.state().session.get(doc).unwrap().measurement_scale(0, line[0]).unwrap();
+        (measure::reading(Kind::Distance, &line, &scale).unwrap().label, scale.ratio)
+    };
+    // Picked from the common scales: no Apply click.
+    h.get_by(|n| n.role() == egui::accesskit::Role::ComboBox && n.value().is_some_and(|v| v == "Common scales")).click();
+    h.run_steps(2);
+    h.get_by_label("1:200").click_accesskit();
+    h.run_steps(3);
+    assert_eq!(read(&h), ("12.00 m".to_string(), "1 mm = 0.2 m".to_string()));
+    // Typed, in the other notations; leaving the field applies.
+    fn field<'a>(h: &'a Harness<'static, PdfCraftApp>) -> egui_kittest::Node<'a> {
+        h.get_by_role_and_label(egui::accesskit::Role::TextInput, "Scale")
+    }
+    for (typed, label) in [("1/50", "3.00 m"), ("1:100", "6.00 m")] {
+        field(&h).click();
+        h.run_steps(1);
+        h.state_mut().views[0].measure.ratio_text.clear();
+        field(&h).type_text(typed);
+        h.run_steps(2);
+        h.key_press(egui::Key::Enter);
+        h.run_steps(3);
+        assert_eq!(read(&h).0, label, "{typed}");
+    }
+    // Nonsense is refused with a message and leaves the page scale alone.
+    let before = read(&h);
+    field(&h).click();
+    h.run_steps(1);
+    h.state_mut().views[0].measure.ratio_text.clear();
+    field(&h).type_text("1:0");
+    h.run_steps(2);
+    h.key_press(egui::Key::Enter);
+    h.run_steps(3);
+    assert_eq!(read(&h), before);
+    assert!(h.state().views[0].measure.error.is_some());
+    // The scale is one undoable edit.
+    ok(&mut h, &c, "ui.command", json!({"id":"edit.undo"}));
+    h.run_steps(2);
+    assert_ne!(read(&h), before);
+}
+
 #[test]
 fn docking_pointer_group_float_close_restore_and_document_commands() {
     use pdfcraft_ui_egui::docking::Panel;
diff --git a/parity/acrobat-features.toml b/parity/acrobat-features.toml
index c06f26e24..423d1814b 100644
--- a/parity/acrobat-features.toml
+++ b/parity/acrobat-features.toml
@@ -4256,7 +4256,7 @@ milestone = "M12"
 status = "partial"
 commands = ["measure.distance"]
 tools = ["measure_distance"]
-evidence = ["crates/automation/tests/automation.rs::measurements_calibrate_draw_save_reopen_and_export", "crates/measure/src/tests.rs::calibrated_lengths_concave_areas_and_axis_scales", "crates/ui-egui/tests/control.rs::measurement_tools_draw_live_calibrate_save_and_export"]
+evidence = ["crates/automation/tests/automation.rs::measurements_calibrate_draw_save_reopen_and_export", "crates/measure/src/tests.rs::calibrated_lengths_concave_areas_and_axis_scales", "crates/ui-egui/tests/control.rs::measurement_tools_draw_live_calibrate_save_and_export", "crates/ui-egui/tests/control.rs::a_plan_scale_picked_or_typed_applies_at_once", "crates/ui-egui/src/measure_ui.rs::typed_ratios_are_read_leniently"]
 notes = "Two-point distance annotations with saved numeric captions and rectilinear scales. Partial: only single-unit decimal formats; compound (ft-in) and fractional formats are not supported (listed as unsupported, data kept), no leader lines or caption placement options, geospatial scales unsupported, and interop with Acrobat-authored measurements (reading theirs, Acrobat reading ours) is untested."
 
 [[feature]]

From 1240c95592948b85a397da5ef7f0add9595ca888 Mon Sep 17 00:00:00 2001
From: Adrien Alberti <adrien@aalberti.com>
Date: Thu, 22 Oct 2026 17:43:59 +0200
Subject: [PATCH 2/2] M12: keep the 1:N field in step with the scale fields;
 review fixes

- ratio_text is derived from the scale fields (one function, sync_ratio_text):
  on page seeding and after a hand edit of drawing points, real distance, unit
  or page unit it shows the matching 1:N, or is emptied when the fields are not
  a plain m/mm drawing scale. The "Common scales" highlight follows it.
- format_ratio no longer rounds (1:1.234, 1:0.001), so the field shows exactly
  the ratio that applies.
- The smallest accepted ratio is 1:0.001, keeping the real distance within the
  minimum of its field; set_ratio refuses out-of-range ratios too.
- "Scale", "Common scales", "Enter a scale such as 1:50." and a hint that
  applying a scale switches units to m / mm are in every i18n catalog, with a
  completeness test.

Co-Authored-By: Claude <noreply@anthropic.com>
---
 crates/ui-egui/src/i18n/ar.tsv      |  4 ++
 crates/ui-egui/src/i18n/bg.tsv      |  4 ++
 crates/ui-egui/src/i18n/ca.tsv      |  4 ++
 crates/ui-egui/src/i18n/ckb.tsv     |  4 ++
 crates/ui-egui/src/i18n/cs.tsv      |  4 ++
 crates/ui-egui/src/i18n/de.tsv      |  4 ++
 crates/ui-egui/src/i18n/el.tsv      |  4 ++
 crates/ui-egui/src/i18n/es.tsv      |  4 ++
 crates/ui-egui/src/i18n/fi.tsv      |  4 ++
 crates/ui-egui/src/i18n/fr.tsv      |  4 ++
 crates/ui-egui/src/i18n/hi.tsv      |  4 ++
 crates/ui-egui/src/i18n/hu.tsv      |  4 ++
 crates/ui-egui/src/i18n/id.tsv      |  4 ++
 crates/ui-egui/src/i18n/it.tsv      |  4 ++
 crates/ui-egui/src/i18n/ja.tsv      |  4 ++
 crates/ui-egui/src/i18n/kk.tsv      |  4 ++
 crates/ui-egui/src/i18n/ko.tsv      |  4 ++
 crates/ui-egui/src/i18n/lo.tsv      |  4 ++
 crates/ui-egui/src/i18n/lt.tsv      |  4 ++
 crates/ui-egui/src/i18n/mod.rs      | 12 ++++
 crates/ui-egui/src/i18n/nb.tsv      |  4 ++
 crates/ui-egui/src/i18n/pl.tsv      |  4 ++
 crates/ui-egui/src/i18n/pt-br.tsv   |  4 ++
 crates/ui-egui/src/i18n/ro.tsv      |  4 ++
 crates/ui-egui/src/i18n/ru.tsv      |  4 ++
 crates/ui-egui/src/i18n/sl.tsv      |  4 ++
 crates/ui-egui/src/i18n/sq.tsv      |  4 ++
 crates/ui-egui/src/i18n/te.tsv      |  4 ++
 crates/ui-egui/src/i18n/th.tsv      |  4 ++
 crates/ui-egui/src/i18n/tr.tsv      |  4 ++
 crates/ui-egui/src/i18n/uk.tsv      |  4 ++
 crates/ui-egui/src/i18n/vi.tsv      |  4 ++
 crates/ui-egui/src/i18n/zh-hans.tsv |  4 ++
 crates/ui-egui/src/i18n/zh-hant.tsv |  4 ++
 crates/ui-egui/src/measure_ui.rs    | 92 ++++++++++++++++++++++++++---
 35 files changed, 229 insertions(+), 7 deletions(-)

diff --git a/crates/ui-egui/src/i18n/ar.tsv b/crates/ui-egui/src/i18n/ar.tsv
index 765bbba55..00e0aeed3 100644
--- a/crates/ui-egui/src/i18n/ar.tsv
+++ b/crates/ui-egui/src/i18n/ar.tsv
@@ -2040,6 +2040,10 @@
 	Perimeter	المحيط
 	Area	المساحة
 	Drawing scale	مقياس الرسم
+	Scale	المقياس
+	Common scales	مقاييس شائعة
+	Enter a scale such as 1:50.	أدخل مقياسًا مثل 1:50.
+	Applying a scale switches units to m / mm.	يؤدي تطبيق المقياس إلى تحويل الوحدات إلى م / مم.
 	Snapping	الانجذاب
 	Export measurements	تصدير القياسات
 	Open a PDF to measure it.	افتح ملف PDF لقياسه.
diff --git a/crates/ui-egui/src/i18n/bg.tsv b/crates/ui-egui/src/i18n/bg.tsv
index 9bb377a93..00f89fa74 100644
--- a/crates/ui-egui/src/i18n/bg.tsv
+++ b/crates/ui-egui/src/i18n/bg.tsv
@@ -1902,6 +1902,10 @@
 	Perimeter	Периметър
 	Area	Площ
 	Drawing scale	Мащаб на чертежа
+	Scale	Мащаб
+	Common scales	Често използвани мащаби
+	Enter a scale such as 1:50.	Въведете мащаб, например 1:50.
+	Applying a scale switches units to m / mm.	Прилагането на мащаб превключва единиците на m / mm.
 	Snapping	Прилепване
 	Export measurements	Експортирай измерванията
 	Open a PDF to measure it.	Отворете PDF файл, за да го измервате.
diff --git a/crates/ui-egui/src/i18n/ca.tsv b/crates/ui-egui/src/i18n/ca.tsv
index 9cad6ad5e..7e5f89039 100644
--- a/crates/ui-egui/src/i18n/ca.tsv
+++ b/crates/ui-egui/src/i18n/ca.tsv
@@ -2000,6 +2000,10 @@ action wizard	Start	Inicia
 	Perimeter	Perímetre
 	Area	Àrea
 	Drawing scale	Escala del dibuix
+	Scale	Escala
+	Common scales	Escales habituals
+	Enter a scale such as 1:50.	Introduïu una escala com 1:50.
+	Applying a scale switches units to m / mm.	En aplicar una escala, les unitats canvien a m / mm.
 	Snapping	Ajust
 	Export measurements	Exporta les mesures
 	Open a PDF to measure it.	Obre un PDF per mesurar-lo.
diff --git a/crates/ui-egui/src/i18n/ckb.tsv b/crates/ui-egui/src/i18n/ckb.tsv
index 804e7a97a..e4a7362c1 100644
--- a/crates/ui-egui/src/i18n/ckb.tsv
+++ b/crates/ui-egui/src/i18n/ckb.tsv
@@ -2003,6 +2003,10 @@
 	Perimeter	چێوە
 	Area	ڕووبەر
 	Drawing scale	پێوەری وێنەکێشان
+	Scale	پێوەر
+	Common scales	پێوەرە باوەکان
+	Enter a scale such as 1:50.	پێوەرێک بنووسە وەک 1:50.
+	Applying a scale switches units to m / mm.	جێبەجێکردنی پێوەر یەکەکان دەگۆڕێت بۆ م / ملم.
 	Snapping	لکاندن
 	Export measurements	هەناردەکردنی پێوانەکان
 	Open a PDF to measure it.	PDFێک بکەرەوە بۆ پێوانەکردنی.
diff --git a/crates/ui-egui/src/i18n/cs.tsv b/crates/ui-egui/src/i18n/cs.tsv
index 4e736bbf4..7da850f2b 100644
--- a/crates/ui-egui/src/i18n/cs.tsv
+++ b/crates/ui-egui/src/i18n/cs.tsv
@@ -2087,6 +2087,10 @@ key	Space	Mezerník
 	Perimeter	Obvod
 	Area	Plocha
 	Drawing scale	Měřítko výkresu
+	Scale	Měřítko
+	Common scales	Běžná měřítka
+	Enter a scale such as 1:50.	Zadejte měřítko, například 1:50.
+	Applying a scale switches units to m / mm.	Použití měřítka přepne jednotky na m / mm.
 	Snapping	Přichytávání
 	Export measurements	Exportovat měření
 	Open a PDF to measure it.	Otevřete PDF, které chcete měřit.
diff --git a/crates/ui-egui/src/i18n/de.tsv b/crates/ui-egui/src/i18n/de.tsv
index 76366d452..1bde60ae1 100644
--- a/crates/ui-egui/src/i18n/de.tsv
+++ b/crates/ui-egui/src/i18n/de.tsv
@@ -1976,6 +1976,10 @@
 	Perimeter	Umfang
 	Area	Fläche
 	Drawing scale	Zeichnungsmaßstab
+	Scale	Maßstab
+	Common scales	Gängige Maßstäbe
+	Enter a scale such as 1:50.	Geben Sie einen Maßstab wie 1:50 ein.
+	Applying a scale switches units to m / mm.	Beim Anwenden eines Maßstabs werden die Einheiten auf m / mm umgestellt.
 	Snapping	Einrasten
 	Export measurements	Messungen exportieren
 	Open a PDF to measure it.	Öffne ein PDF, um es zu messen.
diff --git a/crates/ui-egui/src/i18n/el.tsv b/crates/ui-egui/src/i18n/el.tsv
index 18464664a..7d6922552 100644
--- a/crates/ui-egui/src/i18n/el.tsv
+++ b/crates/ui-egui/src/i18n/el.tsv
@@ -1417,6 +1417,10 @@
 	Perimeter	Περίμετρος
 	Area	Εμβαδόν
 	Drawing scale	Κλίμακα σχεδίου
+	Scale	Κλίμακα
+	Common scales	Συνηθισμένες κλίμακες
+	Enter a scale such as 1:50.	Εισαγάγετε μια κλίμακα, όπως 1:50.
+	Applying a scale switches units to m / mm.	Η εφαρμογή κλίμακας αλλάζει τις μονάδες σε m / mm.
 	Snapping	Προσκόλληση
 	Export measurements	Εξαγωγή μετρήσεων
 	Open a PDF to measure it.	Ανοίξτε ένα PDF για να πραγματοποιήσετε μετρήσεις.
diff --git a/crates/ui-egui/src/i18n/es.tsv b/crates/ui-egui/src/i18n/es.tsv
index db00c69dd..2dfc38749 100644
--- a/crates/ui-egui/src/i18n/es.tsv
+++ b/crates/ui-egui/src/i18n/es.tsv
@@ -2056,6 +2056,10 @@ action wizard	Start	Iniciar
 	Perimeter	Perímetro
 	Area	Área
 	Drawing scale	Escala del dibujo
+	Scale	Escala
+	Common scales	Escalas habituales
+	Enter a scale such as 1:50.	Introduzca una escala como 1:50.
+	Applying a scale switches units to m / mm.	Al aplicar una escala, las unidades cambian a m / mm.
 	Snapping	Ajuste
 	Export measurements	Exportar mediciones
 	Open a PDF to measure it.	Abre un PDF para medirlo.
diff --git a/crates/ui-egui/src/i18n/fi.tsv b/crates/ui-egui/src/i18n/fi.tsv
index 1ddc29982..81b796471 100644
--- a/crates/ui-egui/src/i18n/fi.tsv
+++ b/crates/ui-egui/src/i18n/fi.tsv
@@ -1978,6 +1978,10 @@
 	Perimeter	Ympärysmitta
 	Area	Pinta-ala
 	Drawing scale	Piirustuksen mittakaava
+	Scale	Mittakaava
+	Common scales	Yleiset mittakaavat
+	Enter a scale such as 1:50.	Anna mittakaava, esimerkiksi 1:50.
+	Applying a scale switches units to m / mm.	Mittakaavan käyttö vaihtaa yksiköiksi m / mm.
 	Snapping	Tartunta
 	Export measurements	Vie mittaukset
 	Open a PDF to measure it.	Avaa PDF mitataksesi sitä.
diff --git a/crates/ui-egui/src/i18n/fr.tsv b/crates/ui-egui/src/i18n/fr.tsv
index ec6e59e56..490837d56 100644
--- a/crates/ui-egui/src/i18n/fr.tsv
+++ b/crates/ui-egui/src/i18n/fr.tsv
@@ -1971,6 +1971,10 @@
 	Perimeter	Périmètre
 	Area	Aire
 	Drawing scale	Échelle du dessin
+	Scale	Échelle
+	Common scales	Échelles courantes
+	Enter a scale such as 1:50.	Saisissez une échelle comme 1:50.
+	Applying a scale switches units to m / mm.	Appliquer une échelle passe les unités en m / mm.
 	Snapping	Accrochage
 	Export measurements	Exporter les mesures
 	Open a PDF to measure it.	Ouvrez un PDF pour le mesurer.
diff --git a/crates/ui-egui/src/i18n/hi.tsv b/crates/ui-egui/src/i18n/hi.tsv
index 7be5ec688..bcdcac9a3 100644
--- a/crates/ui-egui/src/i18n/hi.tsv
+++ b/crates/ui-egui/src/i18n/hi.tsv
@@ -1961,6 +1961,10 @@
 	Perimeter	परिमाप
 	Area	क्षेत्रफल
 	Drawing scale	रेखाचित्र पैमाना
+	Scale	पैमाना
+	Common scales	सामान्य पैमाने
+	Enter a scale such as 1:50.	1:50 जैसा पैमाना दर्ज करें।
+	Applying a scale switches units to m / mm.	पैमाना लागू करने पर इकाइयाँ m / mm में बदल जाती हैं।
 	Snapping	स्नैपिंग
 	Export measurements	मापन निर्यात करें
 	Open a PDF to measure it.	मापने के लिए एक पीडीएफ़ खोलें।
diff --git a/crates/ui-egui/src/i18n/hu.tsv b/crates/ui-egui/src/i18n/hu.tsv
index f1723629c..ba244a898 100644
--- a/crates/ui-egui/src/i18n/hu.tsv
+++ b/crates/ui-egui/src/i18n/hu.tsv
@@ -1961,6 +1961,10 @@
 	Perimeter	Kerület
 	Area	Terület
 	Drawing scale	Rajz méretaránya
+	Scale	Méretarány
+	Common scales	Gyakori méretarányok
+	Enter a scale such as 1:50.	Adjon meg egy méretarányt, például 1:50.
+	Applying a scale switches units to m / mm.	A méretarány alkalmazása m / mm mértékegységre vált.
 	Snapping	Illesztés
 	Export measurements	Mérések exportálása
 	Open a PDF to measure it.	Nyiss meg egy PDF-et a méréshez.
diff --git a/crates/ui-egui/src/i18n/id.tsv b/crates/ui-egui/src/i18n/id.tsv
index 3585b344e..58a461382 100644
--- a/crates/ui-egui/src/i18n/id.tsv
+++ b/crates/ui-egui/src/i18n/id.tsv
@@ -1390,6 +1390,10 @@
 	Draw freehand	Gambar bebas
 	Drawing	Gambar
 	Drawing scale	Skala gambar
+	Scale	Skala
+	Common scales	Skala umum
+	Enter a scale such as 1:50.	Masukkan skala seperti 1:50.
+	Applying a scale switches units to m / mm.	Menerapkan skala mengubah satuan menjadi m / mm.
 	Drop-down list	Daftar drop-down
 	Duplicate pages	Duplikat halaman
 	Edit a PDF	Edit PDF
diff --git a/crates/ui-egui/src/i18n/it.tsv b/crates/ui-egui/src/i18n/it.tsv
index 0dc6bb087..49f622af5 100644
--- a/crates/ui-egui/src/i18n/it.tsv
+++ b/crates/ui-egui/src/i18n/it.tsv
@@ -2047,6 +2047,10 @@
 	Perimeter	Perimetro
 	Area	Area
 	Drawing scale	Scala del disegno
+	Scale	Scala
+	Common scales	Scale comuni
+	Enter a scale such as 1:50.	Inserisci una scala come 1:50.
+	Applying a scale switches units to m / mm.	Applicando una scala le unità passano a m / mm.
 	Snapping	Aggancio
 	Export measurements	Esporta misure
 	Open a PDF to measure it.	Apri un PDF per misurarlo.
diff --git a/crates/ui-egui/src/i18n/ja.tsv b/crates/ui-egui/src/i18n/ja.tsv
index 963e8d364..73639521f 100644
--- a/crates/ui-egui/src/i18n/ja.tsv
+++ b/crates/ui-egui/src/i18n/ja.tsv
@@ -2054,6 +2054,10 @@
 	Perimeter	周長
 	Area	面積
 	Drawing scale	図面の縮尺
+	Scale	縮尺
+	Common scales	よく使う縮尺
+	Enter a scale such as 1:50.	1:50 のように縮尺を入力してください。
+	Applying a scale switches units to m / mm.	縮尺を適用すると、単位が m / mm に切り替わります。
 	Snapping	スナップ
 	Export measurements	測定結果を書き出す
 	Open a PDF to measure it.	測定するPDFを開いてください。
diff --git a/crates/ui-egui/src/i18n/kk.tsv b/crates/ui-egui/src/i18n/kk.tsv
index 311626f34..907877336 100644
--- a/crates/ui-egui/src/i18n/kk.tsv
+++ b/crates/ui-egui/src/i18n/kk.tsv
@@ -1962,6 +1962,10 @@
 	Perimeter	Периметр
 	Area	Аудан
 	Drawing scale	Сызба масштабы
+	Scale	Масштаб
+	Common scales	Жиі қолданылатын масштабтар
+	Enter a scale such as 1:50.	1:50 сияқты масштабты енгізіңіз.
+	Applying a scale switches units to m / mm.	Масштабты қолдану өлшем бірліктерін m / mm етіп ауыстырады.
 	Snapping	Түйістіру
 	Export measurements	Өлшемдерді экспорттау
 	Open a PDF to measure it.	Өлшеу үшін PDF құжатын ашыңыз.
diff --git a/crates/ui-egui/src/i18n/ko.tsv b/crates/ui-egui/src/i18n/ko.tsv
index 48ef31e19..bfda232cc 100644
--- a/crates/ui-egui/src/i18n/ko.tsv
+++ b/crates/ui-egui/src/i18n/ko.tsv
@@ -1961,6 +1961,10 @@
 	Perimeter	둘레
 	Area	면적
 	Drawing scale	도면 축척
+	Scale	축척
+	Common scales	자주 쓰는 축척
+	Enter a scale such as 1:50.	1:50과 같은 축척을 입력하세요.
+	Applying a scale switches units to m / mm.	축척을 적용하면 단위가 m / mm로 바뀝니다.
 	Snapping	스냅
 	Export measurements	측정값 내보내기
 	Open a PDF to measure it.	측정할 PDF를 여세요.
diff --git a/crates/ui-egui/src/i18n/lo.tsv b/crates/ui-egui/src/i18n/lo.tsv
index a8a9f6f64..4aa8e4a6d 100644
--- a/crates/ui-egui/src/i18n/lo.tsv
+++ b/crates/ui-egui/src/i18n/lo.tsv
@@ -2014,6 +2014,10 @@
 	Perimeter	ລວງຮອບ
 	Area	ເນື້ອທີ່
 	Drawing scale	ມາດຕາສ່ວນຮູບແຕ້ມ
+	Scale	ມາດຕາສ່ວນ
+	Common scales	ມາດຕາສ່ວນທີ່ໃຊ້ທົ່ວໄປ
+	Enter a scale such as 1:50.	ປ້ອນມາດຕາສ່ວນ ເຊັ່ນ 1:50.
+	Applying a scale switches units to m / mm.	ການນຳໃຊ້ມາດຕາສ່ວນຈະປ່ຽນຫົວໜ່ວຍເປັນ m / mm.
 	Snapping	ການດູດຈັບ
 	Export measurements	ສົ່ງອອກການວັດແທກ
 	Open a PDF to measure it.	ເປີດ PDF ເພື່ອວັດແທກ.
diff --git a/crates/ui-egui/src/i18n/lt.tsv b/crates/ui-egui/src/i18n/lt.tsv
index 0e542211f..2b9d886ec 100644
--- a/crates/ui-egui/src/i18n/lt.tsv
+++ b/crates/ui-egui/src/i18n/lt.tsv
@@ -1449,6 +1449,10 @@
 	Draw freehand	Brėžti laisva ranka
 	Drawing	Brėžinys
 	Drawing scale	Brėžinio mastelis
+	Scale	Mastelis
+	Common scales	Dažni masteliai
+	Enter a scale such as 1:50.	Įveskite mastelį, pavyzdžiui, 1:50.
+	Applying a scale switches units to m / mm.	Pritaikius mastelį, vienetai pakeičiami į m / mm.
 	Drop-down list	Išskleidžiamasis sąrašas
 	Duplicate pages	Dubliuoti puslapius
 	Edit a PDF	Redaguoti PDF
diff --git a/crates/ui-egui/src/i18n/mod.rs b/crates/ui-egui/src/i18n/mod.rs
index dff8efc3d..76d530dc1 100644
--- a/crates/ui-egui/src/i18n/mod.rs
+++ b/crates/ui-egui/src/i18n/mod.rs
@@ -1102,6 +1102,18 @@ mod tests {
         }
     }
 
+    /// The drawing-scale labels of the Measure panel are translated in every catalog.
+    #[test]
+    fn drawing_scale_labels_are_translated_in_every_catalog() {
+        for language in LANGUAGES.iter().filter(|language| !language.source.is_empty()) {
+            let lang = Lang::from_code(language.code).expect("registered language");
+            for label in ["Scale", "Common scales", "Enter a scale such as 1:50.", "Applying a scale switches units to m / mm."] {
+                assert!(has(lang, label), "{} lacks {label:?}", language.code);
+                assert_ne!(tr(lang, label), label, "{} falls back to English for {label:?}", language.code);
+            }
+        }
+    }
+
     /// Every catalog says the labels of a visible signature, which are looked up by the sign
     /// crate's own English words (so the `tl!` scan can't see them), and the note shown when they
     /// fall back to English. Each label that runs into its value keeps a separator at its end.
diff --git a/crates/ui-egui/src/i18n/nb.tsv b/crates/ui-egui/src/i18n/nb.tsv
index 27c1383ec..62a2a9a49 100644
--- a/crates/ui-egui/src/i18n/nb.tsv
+++ b/crates/ui-egui/src/i18n/nb.tsv
@@ -1401,6 +1401,10 @@
 	Draw freehand	Tegn på frihånd
 	Drawing	Tegning
 	Drawing scale	Tegneskala
+	Scale	Målestokk
+	Common scales	Vanlige målestokker
+	Enter a scale such as 1:50.	Skriv inn en målestokk, for eksempel 1:50.
+	Applying a scale switches units to m / mm.	Når du bruker en målestokk, byttes enhetene til m / mm.
 	Drop-down list	Nedtrekksliste
 	Duplicate pages	Dupliser sider
 	Edit a PDF	Rediger en PDF
diff --git a/crates/ui-egui/src/i18n/pl.tsv b/crates/ui-egui/src/i18n/pl.tsv
index cd381b539..c0e0d03eb 100644
--- a/crates/ui-egui/src/i18n/pl.tsv
+++ b/crates/ui-egui/src/i18n/pl.tsv
@@ -2034,6 +2034,10 @@
 	Perimeter	Obwód
 	Area	Pole powierzchni
 	Drawing scale	Skala rysunku
+	Scale	Skala
+	Common scales	Popularne skale
+	Enter a scale such as 1:50.	Wpisz skalę, na przykład 1:50.
+	Applying a scale switches units to m / mm.	Zastosowanie skali zmienia jednostki na m / mm.
 	Snapping	Przyciąganie
 	Export measurements	Eksportuj pomiary
 	Open a PDF to measure it.	Otwórz PDF, aby wykonać pomiar.
diff --git a/crates/ui-egui/src/i18n/pt-br.tsv b/crates/ui-egui/src/i18n/pt-br.tsv
index 8fe72f99b..3e136ff00 100644
--- a/crates/ui-egui/src/i18n/pt-br.tsv
+++ b/crates/ui-egui/src/i18n/pt-br.tsv
@@ -1774,6 +1774,10 @@
 	Perimeter	Perímetro
 	Area	Área
 	Drawing scale	Escala de desenho
+	Scale	Escala
+	Common scales	Escalas comuns
+	Enter a scale such as 1:50.	Digite uma escala como 1:50.
+	Applying a scale switches units to m / mm.	Aplicar uma escala muda as unidades para m / mm.
 	Snapping	Alinhamento inteligente
 	Export measurements	Exportar medições
 	Open a PDF to measure it.	Abra um PDF para medi-lo.
diff --git a/crates/ui-egui/src/i18n/ro.tsv b/crates/ui-egui/src/i18n/ro.tsv
index 5a8025dc8..ef0eb30b9 100644
--- a/crates/ui-egui/src/i18n/ro.tsv
+++ b/crates/ui-egui/src/i18n/ro.tsv
@@ -1399,6 +1399,10 @@
 	Draw freehand	Desenare liberă
 	Drawing	Desen
 	Drawing scale	Scara desenului
+	Scale	Scară
+	Common scales	Scări uzuale
+	Enter a scale such as 1:50.	Introduceți o scară, de exemplu 1:50.
+	Applying a scale switches units to m / mm.	Aplicarea unei scări schimbă unitățile în m / mm.
 	Drop-down list	Listă derulantă
 	Duplicate pages	Duplicare pagini
 	Edit a PDF	Editare PDF
diff --git a/crates/ui-egui/src/i18n/ru.tsv b/crates/ui-egui/src/i18n/ru.tsv
index 0dc40fdba..681a41a2f 100644
--- a/crates/ui-egui/src/i18n/ru.tsv
+++ b/crates/ui-egui/src/i18n/ru.tsv
@@ -2041,6 +2041,10 @@
 	Perimeter	Периметр
 	Area	Площадь
 	Drawing scale	Масштаб чертежа
+	Scale	Масштаб
+	Common scales	Распространённые масштабы
+	Enter a scale such as 1:50.	Введите масштаб, например 1:50.
+	Applying a scale switches units to m / mm.	При применении масштаба единицы переключаются на м / мм.
 	Snapping	Привязка
 	Export measurements	Экспортировать измерения
 	Open a PDF to measure it.	Откройте PDF для измерения.
diff --git a/crates/ui-egui/src/i18n/sl.tsv b/crates/ui-egui/src/i18n/sl.tsv
index f5e374ae7..5fc2c3a62 100644
--- a/crates/ui-egui/src/i18n/sl.tsv
+++ b/crates/ui-egui/src/i18n/sl.tsv
@@ -654,6 +654,10 @@
 	Draw your {what} below.	Spodaj narišite: {what}.
 	Drawing	Risba
 	Drawing scale	Merilo risbe
+	Scale	Merilo
+	Common scales	Pogosta merila
+	Enter a scale such as 1:50.	Vnesite merilo, na primer 1:50.
+	Applying a scale switches units to m / mm.	Z uporabo merila se enote preklopijo na m / mm.
 	Drop PDFs or folders here, or choose them.	Spustite datoteke PDF ali mape sem ali jih izberite.
 	Drop-down list	Spustni seznam
 	Dropdown Properties	Lastnosti spustnega seznama
diff --git a/crates/ui-egui/src/i18n/sq.tsv b/crates/ui-egui/src/i18n/sq.tsv
index c93efee5a..a89c990b2 100644
--- a/crates/ui-egui/src/i18n/sq.tsv
+++ b/crates/ui-egui/src/i18n/sq.tsv
@@ -645,6 +645,10 @@
 	Draw your {what} below.	Vizato {what} më poshtë.
 	Drawing	Vizatim
 	Drawing scale	Shkalla e vizatimit
+	Scale	Shkalla
+	Common scales	Shkalla të zakonshme
+	Enter a scale such as 1:50.	Shkruani një shkallë si 1:50.
+	Applying a scale switches units to m / mm.	Zbatimi i një shkalle i kalon njësitë në m / mm.
 	Drop PDFs or folders here, or choose them.	Hidh PDF ose dosje këtu, ose zgjidh ato.
 	Drop-down list	Listë rënëse
 	Dropdown Properties	Vetitë e listës rënëse
diff --git a/crates/ui-egui/src/i18n/te.tsv b/crates/ui-egui/src/i18n/te.tsv
index fa3f6cec4..3b7d879d5 100644
--- a/crates/ui-egui/src/i18n/te.tsv
+++ b/crates/ui-egui/src/i18n/te.tsv
@@ -1960,6 +1960,10 @@ action wizard	Start	ప్రారంభించు
 	Perimeter	చుట్టుకొలత
 	Area	వైశాల్యం
 	Drawing scale	డ్రాయింగ్ స్కేల్
+	Scale	స్కేల్
+	Common scales	సాధారణ స్కేల్‌లు
+	Enter a scale such as 1:50.	1:50 వంటి స్కేల్‌ను నమోదు చేయండి.
+	Applying a scale switches units to m / mm.	స్కేల్‌ను వర్తింపజేస్తే యూనిట్లు m / mm‌కు మారతాయి.
 	Snapping	స్నాపింగ్
 	Export measurements	కొలతలను ఎగుమతి చేయి
 	Open a PDF to measure it.	కొలవడానికి ఒక PDFను తెరవండి.
diff --git a/crates/ui-egui/src/i18n/th.tsv b/crates/ui-egui/src/i18n/th.tsv
index e56770757..d4c023015 100644
--- a/crates/ui-egui/src/i18n/th.tsv
+++ b/crates/ui-egui/src/i18n/th.tsv
@@ -1984,6 +1984,10 @@
 	Perimeter	เส้นรอบรูป
 	Area	พื้นที่
 	Drawing scale	มาตราส่วนของแบบ
+	Scale	มาตราส่วน
+	Common scales	มาตราส่วนที่ใช้บ่อย
+	Enter a scale such as 1:50.	ป้อนมาตราส่วน เช่น 1:50
+	Applying a scale switches units to m / mm.	การใช้มาตราส่วนจะเปลี่ยนหน่วยเป็น m / mm
 	Snapping	การยึด
 	Export measurements	ส่งออกการวัด
 	Open a PDF to measure it.	เปิด PDF เพื่อวัดระยะ
diff --git a/crates/ui-egui/src/i18n/tr.tsv b/crates/ui-egui/src/i18n/tr.tsv
index c292b8863..64d8aa154 100644
--- a/crates/ui-egui/src/i18n/tr.tsv
+++ b/crates/ui-egui/src/i18n/tr.tsv
@@ -1934,6 +1934,10 @@
 	Perimeter	Çevre
 	Area	Alan
 	Drawing scale	Çizim ölçeği
+	Scale	Ölçek
+	Common scales	Yaygın ölçekler
+	Enter a scale such as 1:50.	1:50 gibi bir ölçek girin.
+	Applying a scale switches units to m / mm.	Ölçek uygulamak birimleri m / mm olarak değiştirir.
 	Snapping	Yakalama
 	Export measurements	Ölçümleri dışa aktar
 	Open a PDF to measure it.	Ölçmek için bir PDF açın.
diff --git a/crates/ui-egui/src/i18n/uk.tsv b/crates/ui-egui/src/i18n/uk.tsv
index cc8f45765..96136a425 100644
--- a/crates/ui-egui/src/i18n/uk.tsv
+++ b/crates/ui-egui/src/i18n/uk.tsv
@@ -2038,6 +2038,10 @@
 	Perimeter	Периметр
 	Area	Площа
 	Drawing scale	Масштаб креслення
+	Scale	Масштаб
+	Common scales	Поширені масштаби
+	Enter a scale such as 1:50.	Введіть масштаб, наприклад 1:50.
+	Applying a scale switches units to m / mm.	Застосування масштабу перемикає одиниці на м / мм.
 	Snapping	Прив’язування
 	Export measurements	Експортувати вимірювання
 	Open a PDF to measure it.	Відкрийте PDF для вимірювання.
diff --git a/crates/ui-egui/src/i18n/vi.tsv b/crates/ui-egui/src/i18n/vi.tsv
index bb20dcc5b..d60a8de88 100644
--- a/crates/ui-egui/src/i18n/vi.tsv
+++ b/crates/ui-egui/src/i18n/vi.tsv
@@ -1439,6 +1439,10 @@ theme	Appearance	Giao diện
 	Draw freehand	Vẽ tự do
 	Drawing	Bản vẽ
 	Drawing scale	Tỷ lệ bản vẽ
+	Scale	Tỷ lệ
+	Common scales	Tỷ lệ thông dụng
+	Enter a scale such as 1:50.	Nhập một tỷ lệ như 1:50.
+	Applying a scale switches units to m / mm.	Áp dụng tỷ lệ sẽ chuyển đơn vị sang m / mm.
 	Drop-down list	Danh sách thả xuống
 	Duplicate pages	Nhân bản trang
 	Edit a PDF	Chỉnh sửa một PDF
diff --git a/crates/ui-egui/src/i18n/zh-hans.tsv b/crates/ui-egui/src/i18n/zh-hans.tsv
index 594f68df8..fc2bb4007 100644
--- a/crates/ui-egui/src/i18n/zh-hans.tsv
+++ b/crates/ui-egui/src/i18n/zh-hans.tsv
@@ -1910,6 +1910,10 @@
 	Perimeter	周长
 	Area	面积
 	Drawing scale	图面比例
+	Scale	比例
+	Common scales	常用比例
+	Enter a scale such as 1:50.	请输入比例，例如 1:50。
+	Applying a scale switches units to m / mm.	应用比例会将单位切换为 m / mm。
 	Snapping	吸附
 	Export measurements	导出测量结果
 	Open a PDF to measure it.	打开 PDF 以进行测量。
diff --git a/crates/ui-egui/src/i18n/zh-hant.tsv b/crates/ui-egui/src/i18n/zh-hant.tsv
index cb578ba26..f0ac381b4 100644
--- a/crates/ui-egui/src/i18n/zh-hant.tsv
+++ b/crates/ui-egui/src/i18n/zh-hant.tsv
@@ -2041,6 +2041,10 @@
 	Perimeter	周長
 	Area	面積
 	Drawing scale	圖面比例
+	Scale	比例
+	Common scales	常用比例
+	Enter a scale such as 1:50.	請輸入比例，例如 1:50。
+	Applying a scale switches units to m / mm.	套用比例會將單位切換為 m / mm。
 	Snapping	吸附
 	Export measurements	匯出測量結果
 	Open a PDF to measure it.	開啟 PDF 以進行測量。
diff --git a/crates/ui-egui/src/measure_ui.rs b/crates/ui-egui/src/measure_ui.rs
index d80ecca3e..658457499 100644
--- a/crates/ui-egui/src/measure_ui.rs
+++ b/crates/ui-egui/src/measure_ui.rs
@@ -115,16 +115,40 @@ pub(crate) fn parse_ratio(text: &str) -> Option<f64> {
         Some((one, n)) => n.trim().parse::<f64>().ok()? / one.trim().parse::<f64>().ok()?,
         None => text.parse::<f64>().ok()?,
     };
-    (n.is_finite() && (1e-6..=1e9).contains(&n)).then_some(n)
+    RATIO_RANGE.contains(&n).then_some(n)
 }
-/// "1:200", or "1:2.5" for a ratio that isn't a whole number.
+/// The N of 1:N this panel accepts. The lower bound keeps the real distance (N / 1000 m) within the
+/// minimum of its field.
+const RATIO_RANGE: std::ops::RangeInclusive<f64> = 1e-3..=1e9;
+/// "1:200", or "1:2.5" for a ratio that isn't a whole number: the number as it is, so the field shows exactly what applies.
 pub(crate) fn format_ratio(n: f64) -> String {
-    let rounded = (n * 100.0).round() / 100.0;
-    if (rounded - rounded.round()).abs() < 1e-9 { format!("1:{}", rounded.round()) } else { format!("1:{rounded}") }
+    format!("1:{n}")
+}
+/// The N of 1:N the scale fields stand for, when they are a plain drawing scale (real distance in m or mm).
+fn ratio_of_fields(state: &MeasureView, display: crate::units::Unit) -> Option<f64> {
+    let real_mm = match state.unit.trim() {
+        "m" => state.real_distance * 1000.0,
+        "mm" => state.real_distance,
+        _ => return None,
+    };
+    let paper_mm = state.drawing_points * page_unit_of(state.page_unit, &state.unit, display).points() * 25.4 / 72.0;
+    let n = real_mm / paper_mm;
+    // Float noise from the unit conversions is rounded away; anything that isn't a clean ratio isn't one.
+    let clean = (n * 1e6).round() / 1e6;
+    (RATIO_RANGE.contains(&clean) && (clean - n).abs() <= 1e-9 * n).then_some(clean)
+}
+/// Make the "1:N" field and the common scale picked in its list say what the scale fields now hold: the ratio, or nothing.
+fn sync_ratio_text(state: &mut MeasureView, display: crate::units::Unit) {
+    state.ratio_text = ratio_of_fields(state, display).map(format_ratio).unwrap_or_default();
+    state.ratio_dirty = false;
+}
+/// What the scale fields hold, to notice a hand edit.
+fn scale_fields(state: &MeasureView) -> (f64, f64, String, Option<PageUnit>) {
+    (state.drawing_points, state.real_distance, state.unit.clone(), state.page_unit)
 }
 /// Fill the scale fields for 1:N: 1 mm on the page is N mm, shown in metres. Returns `false`, changing nothing, when `n` is not a usable ratio.
 pub(crate) fn set_ratio(state: &mut MeasureView, n: f64) -> bool {
-    if !n.is_finite() || n <= 0.0 {
+    if !RATIO_RANGE.contains(&n) {
         return false;
     }
     state.unit = "m".into();
@@ -365,6 +389,7 @@ fn panel_body(app: &mut PdfCraftApp, ui: &mut egui::Ui, _t: &Tokens) {
             state.page_unit = None;
             state.precision = scale.precision;
         }
+        sync_ratio_text(state, units);
     }
     ui.label(tl!("Click vertices. Enter or double-click finishes a perimeter or area. Click the first point to close an area."));
     ui.label(tl!("Shift constrains to 45 degrees. Backspace removes a vertex. Escape cancels."));
@@ -400,8 +425,9 @@ fn panel_body(app: &mut PdfCraftApp, ui: &mut egui::Ui, _t: &Tokens) {
     ui.separator();
     // "1:N" fills the fields below and applies at once, as does picking a common scale.
     let mut chosen = None;
+    let fields = scale_fields(state);
     ui.horizontal(|ui| {
-        ui.label(tl!("Drawing scale"));
+        ui.label(tl!("Drawing scale")).on_hover_text(tl!("Applying a scale switches units to m / mm."));
         let typed = ui.add(crate::widgets::line(&mut state.ratio_text).hint_text("1:100").desired_width(56.0).char_limit(16));
         typed.widget_info(|| egui::WidgetInfo::labeled(egui::WidgetType::TextEdit, true, tl!("Scale")));
         state.ratio_dirty |= typed.changed();
@@ -437,6 +463,10 @@ fn panel_body(app: &mut PdfCraftApp, ui: &mut egui::Ui, _t: &Tokens) {
         ui.add(crate::widgets::line(&mut state.unit).desired_width(64.0).char_limit(12));
         ui.add(egui::DragValue::new(&mut state.precision).range(0..=6).prefix(format!("{} ", tl!("Decimals"))));
     });
+    // A hand edit of the fields leaves the 1:N field showing the old ratio: say the new one.
+    if scale_fields(state) != fields {
+        sync_ratio_text(state, units);
+    }
     if ui.button(tl!("Calibrate from two points")).clicked() {
         tool = Some(Tool::Calibrate);
     }
@@ -597,11 +627,15 @@ mod tests {
         assert_eq!(parse_ratio("250"), Some(250.0));
         assert_eq!(parse_ratio("1:2,5"), Some(2.5));
         assert_eq!(parse_ratio("2:1"), Some(0.5));
+        assert_eq!(parse_ratio("1:0.001"), Some(1e-3));
     }
 
     #[test]
     fn invalid_ratios_are_refused() {
-        for bad in ["", " ", ":", "1:", ":50", "1:0", "0", "-5", "1:-5", "0:5", "abc", "1:abc", "1:50:2", "1:inf", "NaN", "1e12", "1:1e12"] {
+        for bad in [
+            "", " ", ":", "1:", ":50", "1:0", "0", "-5", "1:-5", "0:5", "abc", "1:abc", "1:50:2", "1:inf", "NaN", "1e12", "1:1e12", "1:0.0001",
+            "1:1e-6",
+        ] {
             assert_eq!(parse_ratio(bad), None, "{bad:?}");
         }
     }
@@ -611,6 +645,10 @@ mod tests {
         assert_eq!(format_ratio(50.0), "1:50");
         assert_eq!(format_ratio(2.5), "1:2.5");
         assert_eq!(format_ratio(0.5), "1:0.5");
+        // Nothing is rounded away: the field reads the ratio that applies.
+        assert_eq!(format_ratio(1.234), "1:1.234");
+        assert_eq!(format_ratio(0.001), "1:0.001");
+        assert_eq!(parse_ratio(&format_ratio(333.333333)), Some(333.333333));
         for n in RATIOS {
             assert_eq!(parse_ratio(&format_ratio(n)), Some(n));
         }
@@ -641,6 +679,46 @@ mod tests {
         assert!((v - 0.05).abs() < 1e-9, "{v}");
     }
 
+    #[test]
+    fn the_smallest_ratio_keeps_the_real_distance_within_its_field() {
+        let mut state = MeasureView::default();
+        assert!(set_ratio(&mut state, parse_ratio("1:0.001").expect("ratio")));
+        // The real-distance field accepts 0.000001 and no less.
+        assert!(state.real_distance >= 0.000001, "{}", state.real_distance);
+        assert!(!set_ratio(&mut state, 1e-4));
+    }
+
+    #[test]
+    fn the_ratio_field_follows_the_scale_fields() {
+        let display = crate::units::Unit::Points;
+        let mut state = MeasureView::default();
+        for n in [50.0, 2.5, 1.234, 0.001, 1e9] {
+            assert!(set_ratio(&mut state, n));
+            sync_ratio_text(&mut state, display);
+            assert_eq!(state.ratio_text, format_ratio(n), "1:{n}");
+        }
+        // A hand edit that is still a drawing scale reads as its ratio, in another page unit too.
+        assert!(set_ratio(&mut state, 50.0));
+        state.page_unit = Some(PageUnit::Cm);
+        sync_ratio_text(&mut state, display);
+        assert_eq!(state.ratio_text, "1:5");
+        state.page_unit = Some(PageUnit::Mm);
+        state.real_distance = 0.1;
+        sync_ratio_text(&mut state, display);
+        assert_eq!(state.ratio_text, "1:100");
+        // One that isn't (another unit, or no ratio at all) empties it.
+        state.unit = "ft".into();
+        sync_ratio_text(&mut state, display);
+        assert_eq!(state.ratio_text, "");
+        state.unit = "m".into();
+        state.real_distance = 0.1 / 3.0;
+        sync_ratio_text(&mut state, display);
+        assert_eq!(state.ratio_text, "");
+        state.drawing_points = 0.0;
+        sync_ratio_text(&mut state, display);
+        assert_eq!(state.ratio_text, "");
+    }
+
     #[test]
     fn an_unusable_ratio_changes_nothing() {
         let mut state = MeasureView::default();