Group Expense Settle-Up

On a group trip nobody pays for everything and nobody pays for nothing: one person books the hotel, another fills the tank, a third covers Saturday dinner. By the end the question is not how much each person spent, it is who transfers what to whom. This page does that arithmetic. You write one expense per line — who paid, how much, what for — and it returns three things: the group total, how much each person paid against what they owed, and the list of transfers that brings everyone to zero. Anyone who took part but never paid goes in the field below, comma separated, otherwise the split runs short of people and comes out wrong.

Two calculation decisions are worth stating. The first is that money moves in whole cents, never in fractions: adding 0.10 to 0.20 in floating point returns 0.30000000000000004, and in a settle-up that residue shows up as a cent that vanishes or appears out of nowhere. The second is what to do when the division is not exact. One hundred split three ways is 33.33 with one cent left over, and that cent has to land on somebody or the total no longer adds back to a hundred. This page rotates the leftover from expense to expense rather than always handing it to the first name on the list, so the same person does not eat the extra cent on every bill of the trip.

Not every expense belongs to everyone, which is what the greater-than sign is for. Writing the taxi line followed by that sign and the names of whoever was in the car limits that expense to those people; without it, the expense is split across the whole group. About the transfers: the page matches the largest debtor with the largest creditor until one of them clears, which yields at most one transfer fewer than the number of people. That handles everyday cases well, but it is not guaranteed to be the smallest possible number of payments, which is a hard problem to solve exactly. What the page does guarantee is that once every transfer on the list is made, nobody owes anybody anything.