diff --git a/shared/src/book/book-findings.ts b/shared/src/book/book-findings.ts
index 433ea8a77..543d5c005 100644
--- a/shared/src/book/book-findings.ts
+++ b/shared/src/book/book-findings.ts
@@ -76,7 +76,12 @@ export function photoDpi(el: BookPhotoElement, info: BookPhotoInfo | undefined):
 }
 
 /** Average letter width per em at weight 400, per family: the catalogue's measure (book-fonts.data.ts). */
-const letterEm = (font: string) => bookFontFace(font)?.letterEm ?? 0.5;
+/** A family's average letter width per em at a weight: its measured bold from 600 on, else a guess a little wider. */
+function letterEm(font: string, weight: number): number {
+  const face = bookFontFace(font);
+  const regular = face?.letterEm ?? 0.5;
+  return weight >= 600 ? (face?.boldEm ?? regular * 1.06) : regular;
+}
 
 /**
  * The headroom on letter width the design engine sizes a text frame with. A
@@ -124,7 +129,7 @@ export function bookLetterMm(el: BookTextElement, headroom = 1): number {
   const sizeMm = (orDefault(el.size, 11) * 25.4) / 72;
   const tracking = orDefault(el.tracking, 0);
   const caps = bookFontFace(el.font)?.caps ? 1 : (CASE_WIDTH[el.transform ?? 'none'] ?? 1);
-  return sizeMm * (letterEm(el.font) * (el.weight >= 600 ? 1.06 : 1) * caps * headroom + tracking);
+  return sizeMm * (letterEm(el.font, el.weight) * caps * headroom + tracking);
 }
 
 /**
diff --git a/shared/src/book/book-fonts.data.ts b/shared/src/book/book-fonts.data.ts
index fb85f2398..1f7abdd6c 100644
--- a/shared/src/book/book-fonts.data.ts
+++ b/shared/src/book/book-fonts.data.ts
@@ -58,6 +58,11 @@ export interface BookFontFace {
    * the face's own advance widths, for the text measure in book-findings.ts.
    */
   letterEm: number;
+  /**
+   * The same at weight 700, measured the same way, for a family that ships a
+   * real bold: a condensed bold sets up to a sixth wider than its regular.
+   */
+  boldEm?: number;
   /** Set in capitals whatever is typed. */
   caps?: true;
 }
@@ -81,6 +86,7 @@ export const BOOK_FONT_FACES = {
     weights: ALL,
     italics: [],
     letterEm: 0.507,
+    boldEm: 0.519,
   },
   inter: {
     name: 'Inter',
@@ -91,6 +97,7 @@ export const BOOK_FONT_FACES = {
     weights: ALL,
     italics: [],
     letterEm: 0.478,
+    boldEm: 0.491,
   },
   montserrat: {
     name: 'Montserrat',
@@ -101,6 +108,7 @@ export const BOOK_FONT_FACES = {
     weights: ALL,
     italics: [],
     letterEm: 0.507,
+    boldEm: 0.536,
   },
   // ── serif ──
   serif: {
@@ -112,6 +120,7 @@ export const BOOK_FONT_FACES = {
     weights: MID,
     italics: MID,
     letterEm: 0.469,
+    boldEm: 0.481,
   },
   garamond: {
     name: 'EB Garamond',
@@ -122,6 +131,7 @@ export const BOOK_FONT_FACES = {
     weights: [400, 500, 600, 700, 800],
     italics: [400, 500, 600, 700, 800],
     letterEm: 0.383,
+    boldEm: 0.424,
   },
   // ── elegant display serifs ──
   playfair: {
@@ -133,6 +143,7 @@ export const BOOK_FONT_FACES = {
     weights: [400, 500, 600, 700, 800, 900],
     italics: [400, 500, 600, 700, 800, 900],
     letterEm: 0.454,
+    boldEm: 0.462,
   },
   fraunces: {
     name: 'Fraunces',
@@ -143,6 +154,7 @@ export const BOOK_FONT_FACES = {
     weights: ALL,
     italics: ALL,
     letterEm: 0.467,
+    boldEm: 0.497,
   },
   cormorant: {
     name: 'Cormorant Garamond',
@@ -153,6 +165,7 @@ export const BOOK_FONT_FACES = {
     weights: [300, 400, 500, 600, 700],
     italics: [300, 400, 500, 600, 700],
     letterEm: 0.393,
+    boldEm: 0.398,
   },
   dmserif: {
     name: 'DM Serif Display',
@@ -173,6 +186,7 @@ export const BOOK_FONT_FACES = {
     weights: [400, 500, 600, 700, 800, 900],
     italics: [400, 500, 600, 700, 800, 900],
     letterEm: 0.463,
+    boldEm: 0.488,
   },
   // ── condensed and poster ──
   bebas: {
@@ -205,6 +219,7 @@ export const BOOK_FONT_FACES = {
     weights: [200, 300, 400, 500, 600, 700],
     italics: [],
     letterEm: 0.365,
+    boldEm: 0.412,
   },
   league: {
     name: 'League Gothic',
@@ -225,6 +240,7 @@ export const BOOK_FONT_FACES = {
     weights: ALL,
     italics: [],
     letterEm: 0.304,
+    boldEm: 0.355,
   },
   archivo: {
     name: 'Archivo Black',
@@ -246,6 +262,7 @@ export const BOOK_FONT_FACES = {
     weights: ALL,
     italics: [],
     letterEm: 0.492,
+    boldEm: 0.5,
   },
   shrikhand: {
     name: 'Shrikhand',
@@ -276,6 +293,7 @@ export const BOOK_FONT_FACES = {
     weights: [200, 300, 400, 500, 600, 700, 800],
     italics: [],
     letterEm: 0.471,
+    boldEm: 0.49,
   },
   abril: {
     name: 'Abril Fatface',
@@ -297,6 +315,7 @@ export const BOOK_FONT_FACES = {
     weights: MID,
     italics: [],
     letterEm: 0.344,
+    boldEm: 0.349,
   },
   dancing: {
     name: 'Dancing Script',
@@ -307,6 +326,7 @@ export const BOOK_FONT_FACES = {
     weights: MID,
     italics: [],
     letterEm: 0.363,
+    boldEm: 0.372,
   },
   pacifico: {
     name: 'Pacifico',
diff --git a/shared/src/book/book-fonts.spec.ts b/shared/src/book/book-fonts.spec.ts
index 63d786f09..5e807e9e1 100644
--- a/shared/src/book/book-fonts.spec.ts
+++ b/shared/src/book/book-fonts.spec.ts
@@ -71,6 +71,12 @@ describe('the catalogue', () => {
       for (const w of face.italics) expect(face.weights, `${id} italic ${w}`).toContain(w);
       expect(face.letterEm, id).toBeGreaterThan(0.2);
       expect(face.letterEm, id).toBeLessThan(0.7);
+      // A measured bold only where the family ships one, and never narrower than its regular.
+      const bold = (face as { boldEm?: number }).boldEm;
+      if (bold !== undefined) {
+        expect(face.weights as readonly number[], id).toContain(700);
+        expect(bold, id).toBeGreaterThanOrEqual(face.letterEm);
+      }
       expect(face.roles.length, id).toBeGreaterThan(0);
     }
   });
diff --git a/shared/src/book/book-text-fit.spec.ts b/shared/src/book/book-text-fit.spec.ts
index f51486af2..ed3251cee 100644
--- a/shared/src/book/book-text-fit.spec.ts
+++ b/shared/src/book/book-text-fit.spec.ts
@@ -1,4 +1,4 @@
-import { textHeightNeeded } from './book-findings';
+import { bookLetterMm, textHeightNeeded } from './book-findings';
 import { blankBook } from './book-pages';
 import {
   bookCasedText,
@@ -138,4 +138,12 @@ describe('fitting a page', () => {
     expect((next.spreads[0]?.elements[0] as BookTextElement).size).toBeLessThan(60);
     expect(next.spreads[1]).toBe(doc.spreads[1]);
   });
+
+  it('BKFIT-011: a bold condensed face is measured at its own width, not the regular widened by a guess', () => {
+    const oswald = (weight: number) => bookLetterMm(text({ font: 'oswald', weight, size: 20 }));
+    // Oswald's 700 sets about 13% wider than its 400; a flat 6% would let a bold heading overrun its frame.
+    expect(oswald(700) / oswald(400)).toBeGreaterThan(1.1);
+    const vibes = (weight: number) => bookLetterMm(text({ font: 'vibes', weight, size: 20 }));
+    expect(vibes(700) / vibes(400)).toBeCloseTo(1.06, 6);
+  });
 });