diff --git a/CHANGES.md b/CHANGES.md
index 9c38282..5d8762f 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,6 +1,7 @@
 # Changes
 
 ## Unreleased
+- Add splitBill(items, people): splits total() into per-person shares that add up exactly.
 
 ## 1.2.0
 - total() rounds through roundCents().
diff --git a/src/lib/cart.js b/src/lib/cart.js
index 385fd69..f0ddd39 100644
--- a/src/lib/cart.js
+++ b/src/lib/cart.js
@@ -8,3 +8,16 @@ export function subtotal(items) {
 export function total(items) {
   return roundCents(subtotal(items) * (1 + TAX_RATE));
 }
+
+// `people` is a head count or an array of people. Shares are whole cents that add up
+// exactly to total(items); leftover cents go one each to the first people.
+export function splitBill(items, people) {
+  const count = Array.isArray(people) ? people.length : people;
+  if (!Number.isInteger(count) || count < 1) {
+    throw new RangeError('splitBill needs at least one person');
+  }
+  const totalCents = roundCents(total(items) * 100);
+  const base = Math.trunc(totalCents / count);
+  const extra = totalCents - base * count;
+  return Array.from({ length: count }, (_, i) => (base + (i < extra ? 1 : 0)) / 100);
+}
diff --git a/tests/lib/cart.test.js b/tests/lib/cart.test.js
index 7a9eab3..456b9dc 100644
--- a/tests/lib/cart.test.js
+++ b/tests/lib/cart.test.js
@@ -1,6 +1,7 @@
 import { test } from 'node:test';
 import assert from 'node:assert/strict';
-import { subtotal, total } from '../../src/lib/cart.js';
+import { subtotal, total, splitBill } from '../../src/lib/cart.js';
+import { roundCents } from '../../src/lib/money.js';
 
 const items = [{ price: 10, qty: 2 }, { price: 5, qty: 1 }];
 
@@ -11,3 +12,41 @@ test('subtotal adds price times quantity', () => {
 test('total applies tax and rounds to cents', () => {
   assert.equal(total(items), 27);
 });
+
+test('splitBill splits the taxed total evenly', () => {
+  assert.deepEqual(splitBill(items, ['a', 'b']), [13.5, 13.5]);
+});
+
+test('splitBill accepts a head count instead of a list', () => {
+  assert.deepEqual(splitBill(items, 3), [9, 9, 9]);
+});
+
+test('splitBill gives one person the whole total', () => {
+  assert.deepEqual(splitBill(items, ['a']), [27]);
+});
+
+test('splitBill hands leftover cents to the first people', () => {
+  // 1.01 * 1.08 = 1.09 -> 0.37, 0.36, 0.36
+  assert.deepEqual(splitBill([{ price: 1.01, qty: 1 }], 3), [0.37, 0.36, 0.36]);
+});
+
+test('splitBill shares always add up to the total', () => {
+  const cart = [{ price: 10, qty: 1 }];
+  const shares = splitBill(cart, 7);
+  assert.equal(shares.length, 7);
+  assert.equal(roundCents(shares.reduce((a, b) => a + b, 0)), total(cart));
+});
+
+test('splitBill on an empty cart returns zero shares', () => {
+  assert.deepEqual(splitBill([], 2), [0, 0]);
+});
+
+test('splitBill with more people than cents leaves some with zero', () => {
+  assert.deepEqual(splitBill([{ price: 0.01, qty: 1 }], 3), [0.01, 0, 0]);
+});
+
+test('splitBill rejects zero, negative, fractional, or empty people', () => {
+  for (const bad of [0, -1, 1.5, [], undefined, NaN]) {
+    assert.throws(() => splitBill(items, bad), RangeError);
+  }
+});