Splitting trip costs fairly: shares, currencies and settling up
A shared trip produces a pile of receipts paid by different people, for different people, in different currencies. Four decisions turn that pile into a short list of who pays whom.
1. Record who paid, and who it was for
Every expense needs both. “Ana paid for the flat” is half the story; the other half is that the flat was for all three of them. Most expenses are for everyone, but not all — a tour two people took, a taxi that dropped two people off.
There are three honest ways to divide one expense:
- Equally between the people it was for.
- By shares, when some people should pay more: a couple taking two places counts 2, a single traveller 1.
- By exact amounts, when each person's part is known from the bill.
2. Keep each expense in the currency it was paid in
Convert once, at the end, at one rate you choose — ideally the rate on the card or bank statement, because that is what was really paid. Converting each receipt on the day with a different online rate produces totals nobody's bank agrees with. And if a rate is missing, leave the expense out of the totals until it is entered; a guessed rate is a quiet error in everyone's balance.
3. Work out balances: paid minus share
Three friends in Lisbon. Their home currency is the US dollar, and the euro cost them $1.10:
| Expense | Paid by | For | In dollars |
|---|---|---|---|
| Flat, $600 | Ana | Everyone, equally | $600.00 |
| Dinner, €90 | Ben | Everyone, equally | $99.00 |
| Tour, $120 | Cy | Ana 2 shares, Ben 1 | $120.00 |
| Taxi, €30 | Ana | Ben €20, Cy €10 | $33.00 |
| The trip | $852.00 |
| Person | Paid | Their share | Balance |
|---|---|---|---|
| Ana | $633.00 | $313.00 | is owed $320.00 |
| Ben | $99.00 | $295.00 | owes $196.00 |
| Cy | $120.00 | $244.00 | owes $124.00 |
The balances always add up to zero: every dollar someone is owed is a dollar someone else owes.
4. Settle in as few payments as possible
Paying back expense by expense would take a payment for almost every receipt. Settling the balances instead takes at most one payment fewer than the number of people: here Ben pays Ana $196.00 and Cy pays Ana $124.00, and everyone is square. When a payment is made, record it as a repayment — it moves the balances, but it is not something the trip cost.
Where do the odd cents go?
$100 split three ways is $33.333… each, which cannot be paid. Rounding everyone to $33.33 loses a cent; rounding up to $33.34 invents two. The fair fix is to give everyone the rounded-down amount and hand the leftover cents, one at a time, to whoever had the largest remainder: $33.34, $33.33 and $33.33 — exactly $100.
Your own share, for your own records
What you spent on a trip is your share, not what you happened to pay — Ana paid $633 but her trip cost her $313. That share is the figure worth keeping in a yearly budget.