Split expenses with friends and see who owes who

How to split trip costs between friends

Splitting a trip fairly comes down to one sum per person: what they paid, minus their share of everything. If the answer is positive, the group owes them; if it is negative, they owe the group. The calculator keeps that sum for everyone as you add expenses.

1. Add the people. Everyone who shares any cost, including whoever is typing.
2. Add each expense once, with the person who actually paid. If two people paid for the same thing, add two expenses.
3. Choose how it is shared. Equally between everyone, equally between some people only, by shares, or by exact amounts.
4. Read the result. The plate shows everyone’s balance and the transfers that settle the group, with the full ledger underneath.

A worked example: a weekend for four

The example already on the page is a weekend at a lake cabin. Alex booked the cabin for €480.00, Bea bought €93.17 of groceries, Chen paid €61.40 for fuel and €45.00 for wine, and Dee paid €154.00 for dinner at the pub.

Equally, by shares, exact amounts or some people only

• Equally suits shared things everyone used: the accommodation, the communal shop, a taxi you all took.
• Some people only: untick anyone who wasn’t in on it. Dee came by train, so the fuel is split between the other three.
• By shares handles “twice as much” without arithmetic. Bea and Dee drank most of the wine, so they have 2 shares each and Alex and Chen 1: six shares of €7.50.
• Exact amounts is for itemised bills such as a restaurant where everyone ordered differently. The amounts must add up to the total; the form tells you how much is still unassigned.

Where the odd cent goes

€93.17 does not divide by four: each quarter is €23.2925. Every share is rounded down to the cent (€23.29), which leaves one cent over. Leftover cents go one each to the people whose shares lost most in the rounding, and when those are equal, to whoever is higher in the people list. So Alex pays €23.30 and everyone else €23.29. Nobody ever pays more than one extra cent on an expense, and the shares always add up to the exact total. The plate lists every expense that needed rounding and who covered the cent.

How the fewest transfers are found

Once the balances are known, the money still has to move. Paying each other back expense by expense can take dozens of transfers; settling the balances takes far fewer. The calculator first pairs off anyone who owes exactly what someone else is owed. Then, again and again, the person who owes the most pays the person owed the most, as much as clears one of them. Each step settles at least one person, so a group of n people never needs more than n − 1 transfers.

That is the fewest possible in most groups, but not in every case. Finding the true minimum means finding the most separate subgroups whose balances cancel out, and Tom Verhoeff showed that this version of the problem is NP-hard: no known method solves every large case quickly. A small example where the shortcut misses: Amy is owed €60 and Ben €40, while Cara and Dan owe €30 each and Eve and Finn €20 each. Cara and Dan could pay Amy, and Eve and Finn pay Ben: four transfers. The largest-to-largest rule finds five. For a group of friends the difference is rarely more than one transfer.

Sharing the tally with friends

The share link holds the whole tally after the # in the address, compressed. Browsers keep that part of a link to themselves: it is not sent to the web server when the page loads, so your expenses never reach us. Anyone who opens the link sees the same figures and can add to them; send the new link back to share their changes.

Long tallies make long links. Web standards ask software to cope with addresses of at least 8,000 characters, but chat and email apps vary, so above 2,000 characters (our own cautious limit) the page suggests sending the CSV file instead. The CSV opens in any spreadsheet: one row per expense with Description, Amount, Paid by and Split, then one column per person holding a 1 for an equal split, a number of shares, or an exact amount. Import it here to carry on.

Your tally is also saved in this browser, so it is still there when you come back. Start a new tally to clear it.

Common mistakes

• Leaving the payer out of the split. If Alex pays for four people’s dinner, Alex is one of the four. Untick the payer only if the expense really was a gift or wasn’t theirs.
• Adding a refund as a new expense. If part of a booking came back, edit the original amount instead.
• Mixing currencies. The calculator does not convert. Turn everything into one currency first, at the rate you actually paid.
• Settling expense by expense. Five people paying each other back for twenty receipts can take forty transfers. Settle the balances once, at the end.

Renting a cottage for several nights where people come and go? The holiday house cost split shares a booking by nights and room size and sends the result back here.