Penny-accurate splitting

When you split £10.00 between 3 people, each person's share is £3.333... — which is not a valid amount. Most apps round this to £3.33, but 3 × £3.33 = £9.99. A penny goes missing.

Over many expenses, these missing pennies add up. Settled Up makes sure this never happens.

Every amount in Settled Up is stored in the smallest unit of the currency (pence for GBP, cents for EUR/USD). When splitting £10.00 between 3 people:

1. 1 1000 pence ÷ 3 = 333 pence each, with 1 penny remaining.
2. 2 Two people get £3.33. One person gets £3.34.
3. 3 Total: £3.33 + £3.33 + £3.34 = £10.00. Every penny accounted for.

You might wonder: who gets the extra penny? If it always went to the same person, that would not be fair.

Settled Up uses a deterministic shuffle based on each expense. For every expense, the participants are sorted in a different order using a mathematical hash. The remainder pennies go to whoever lands first in that order.

This means the extra penny rotates fairly across different expenses. Over a tab with many expenses, no one consistently pays more or less than anyone else.

If you compare your total share with someone else's across a whole tab, you might notice a small difference — typically a few pence. This is the accumulated effect of remainder distribution across many expenses.

You can see your exact share on your personal ledger, which shows "Your share (X of Y expenses)" — confirming exactly how many expenses you were included in and what your total share was.