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Two payments settle a $1,845.00 shared cost. Enter the cost, what each person already paid, and how it should be divided. This cost splitter works out each person's fair share, whether they are owed or still owe, and the payments that square the whole thing - no app, no account, nothing stored.
Settlement for a $1,845.00 shared cost, split equally between 3 people
2 payments: C pays A $390.00, B pays A $195.00
In weight mode each person's weight is their share of the basis - room size in square feet, nights in the house, or income. Weights of 180 / 140 / 100 split the cost in that ratio. Leave them at 1 to fall back to equal shares.
Every share is worked out in whole cents: the cost is divided, each share is rounded down, and the leftover cents go to the largest fractional parts, so the shares always add back to the cost exactly.
Three bars, one marker: each bar is what that person already paid, the marker is their fair share, and the distance between the two is what still has to move.
The figure above shows one case; this table runs the same arithmetic on five. Every row can be re-checked against the calculator at the top of the page by typing the cost and the paid amounts in.
| Case | Fair shares | Payments that square it | Moves |
|---|---|---|---|
| Three people, paid $1,200.00 / $420.00 / $225.00, equally | $615.00 each | C pays A $390.00; B pays A $195.00 | $585.0031.71% |
| Same cost, same payments, by room size 180 / 140 / 100 sq ft | $790.71 / $615.00 / $439.29 | C pays A $214.29; B pays A $195.00 | $409.2922.18% |
| Four people, paid $900.00 / $500.00 / $300.00 / $145.00, equally | $461.25 each | D pays A $316.25; C pays A $122.50; C pays B $38.75 | $477.5025.88% |
| Two people, paid $1,200.00 / $645.00, equally | $922.50 each | B pays A $277.50 | $277.5015.04% |
| One person paid the whole $1,845.00, equally | $615.00 each | B pays A $615.00; C pays A $615.00 | $1,230.0066.67% |
The figure in the last column is the amount of the cost that actually changes hands, and the percentage under it is that amount as a share of the cost.
Almost none of a shared cost has to be re-settled, because what has already been paid is netted off against the shares first. In the default case B and C between them paid $645.00 while their two shares come to $1,230.00, so $585.00 of their obligation is still outstanding - and that is exactly the amount that has to change hands, 31.71% of the cost. Where the payments land close to the fair shares the figure collapses towards zero - three payments of exactly $615.00 leave nothing to settle at all - and where one person carries the whole cost it climbs towards the whole amount: the last row of the table moves $1,230.00, two thirds of the cost, because the other two have not paid a cent yet.
Switching from equal shares to room size changes who owes whom as well as how much. The same $1,845.00 and the same three payments give $615.00 each on an equal split, and $790.71 / $615.00 / $439.29 on a 180 / 140 / 100 square-foot split. A's position falls from $585.00 owed to $409.29 owed, C's from $390.00 owed to $214.29, and the money that actually changes hands drops from $585.00 to $409.29 - $175.71 less, 30.03% of what would have moved. That is the whole argument for agreeing the basis before the money moves: it is not a rounding difference, it is $175.71 of transfers.
The settlement takes the person who is owed the most and the person who owes the most, and settles as much of that pair as possible, then repeats. That is why the default case produces two payments rather than three: the largest debt, C's $390.00, is taken out of the largest credit, A's $585.00, in one go, and the smaller debt of $195.00 clears the rest. The rule does not guarantee the fewest possible payments in every arrangement, but on the shapes that actually come up - one person carrying most of a cost, or everyone paying a different amount - it lands on the natural answer.
The two numbers are separate inputs on purpose: the cost is what the thing cost, and the paid column is what has actually changed hands so far. When they disagree the split is still worked out on the cost, because the cost is the thing being divided.
If the payments add up to $1,895.00 against a $1,845.00 cost, the shares are unchanged at $615.00 each and the positions become +$585.00 / -$195.00 / -$340.00. Two payments of $340.00 and $195.00 still square the cost, and $535.00 moves. The extra $50.00 is not part of the split at all - it stays wherever it was paid in, and the page says so on the warning line rather than quietly absorbing it.
If the payments add up to $1,795.00, the same cost still splits into $615.00 each, and the settlement runs C pays A $440.00 and B pays A $145.00. The positions then add up to -$50.00 rather than zero, because $50.00 of the cost has not been paid by anybody yet. Every transfer still lands on the right person; the shortfall is the part that has to be paid in later, and the warning line names the amount.
An empty paid column is the "who owes what" case rather than the "who pays whom" case: the shares come out at $615.00 each and there is nothing to settle, because nothing has been laid out. The same page answers both questions - what each person's fair share is, and, once money has moved, who has to hand what to whom.
A calculator that takes one shared cost and the people who share it, and answers two questions: what is each person's fair share, and, when the payments already made are uneven, who pays whom to square it. A restaurant bill is one kind of shared cost; a replacement appliance or a deposit that one person put on a card is another, and the second kind is the one that needs settling rather than just dividing.
Work out the fair share first, then compare it with what each person actually paid. On a $1,845.00 cost split three ways the fair share is $615.00 each. If A paid $1,200.00, B $420.00 and C $225.00, A is $585.00 up, B is $195.00 down and C is $390.00 down, so C pays A $390.00 and B pays A $195.00. Everybody ends up having paid exactly $615.00.
Use each room's size as the weight and the cost follows the ratio. On a $1,845.00 cost with rooms of 180, 140 and 100 square feet the weights add to 420, and the shares are $790.71, $615.00 and $439.29 - which is $1,845.00 x 180/420, x 140/420 and x 100/420, rounded down with the leftover cent going to the largest fractional part. Any basis works the same way: nights in the house, income, or the number of people a room sleeps.
The split is still worked out on the cost, because that is the thing being divided. If the payments come to more than the cost, the extra stays with whoever paid it in; if they come to less, the shortfall is the part of the cost nobody has covered yet. Both cases are named on the warning line with the exact figure, so the difference is visible instead of buried in the totals.
No, and the calculator does not decide it for you. Equal shares are the default because they are the easiest to agree to; weight mode exists for the cases where the basis is room size, nights or income. What the page does is take whichever basis you point it at and work out the shares and the settlement from it exactly - it does not choose the basis, and it stores nothing.
Each person with a balance owing pays the person with the largest balance owed, until the largest debt is cleared, and then the next. That is why a three-person split with one payer ahead usually needs two payments rather than three. On the default case the largest debt of $390.00 is settled against the largest credit of $585.00 first, and the remaining $195.00 debt clears the rest of the credit.