diff --git a/src/sim/money.ts b/src/sim/money.ts
new file mode 100644
index 0000000..b21abcb
--- /dev/null
+++ b/src/sim/money.ts
@@ -0,0 +1,18 @@
+import { GameDate, isEuroEra } from './calendar';
+
+export const FRANCS_PER_EURO = 6.55957;
+
+export function francsToCents(francs: number): number {
+  return Math.round((francs / FRANCS_PER_EURO) * 100);
+}
+
+export function centsToFrancs(cents: number): number {
+  return (cents / 100) * FRANCS_PER_EURO;
+}
+
+export function formatMoney(cents: number, date: GameDate): string {
+  const euro = isEuroEra(date);
+  const value = euro ? cents / 100 : centsToFrancs(cents);
+  const text = value.toFixed(2).replace('.', ',');
+  return euro ? `${text} €` : `${text} F`;
+}
diff --git a/tests/sim/money.test.ts b/tests/sim/money.test.ts
new file mode 100644
index 0000000..dd2c165
--- /dev/null
+++ b/tests/sim/money.test.ts
@@ -0,0 +1,26 @@
+import { describe, it, expect } from 'vitest';
+import { centsToFrancs, formatMoney, francsToCents } from '../../src/sim/money';
+
+describe('money', () => {
+  it('converts francs to euro cents at the fixed rate', () => {
+    expect(francsToCents(249)).toBe(3796);
+    expect(francsToCents(199)).toBe(3034);
+    expect(francsToCents(0)).toBe(0);
+  });
+
+  it('converts cents back to francs', () => {
+    expect(centsToFrancs(3796)).toBeCloseTo(249, 1);
+  });
+
+  it('formats in francs before 2002', () => {
+    expect(formatMoney(3796, { year: 1990, month: 9, day: 28 })).toBe('249,00 F');
+  });
+
+  it('formats in euros from 2002', () => {
+    expect(formatMoney(3796, { year: 2002, month: 1, day: 1 })).toBe('37,96 €');
+  });
+
+  it('formats negative amounts', () => {
+    expect(formatMoney(-3796, { year: 2002, month: 1, day: 1 })).toBe('-37,96 €');
+  });
+});