Splitting a bill with a tip
The arithmetic is simple enough — tip on the total, add it, divide by heads — but it's the bit everyone gets wrong at the table after a couple of drinks. A $120 bill at 18% is $21.60 of tip, $141.60 all in, $35.40 each between four.
Two things worth knowing. Tipping pre-tax or post-tax barely matters: on a $100 bill with 10% tax, 20% pre-tax is $20 and post-tax is $22, so the argument is over 50 cents a head. And rounding up is the norm rather than the exception — the round-up option here pushes each share to a whole unit and shows you what that does to the effective tip, which is usually a percentage point or two.
The bit most calculators get wrong
Dividing a total by the number of people is easy enough to do in your head. The part that actually causes arguments is when several people paid different amounts — you covered the hotel, someone else got the car, a third person bought all the groceries — and now nobody can work out who settles with whom.
That's the second tab. Enter what each person paid and the calculator works out what each person should owe, then computes the fewest payments that clear every debt. If four people owe each other in a tangle, it usually collapses to two or three transfers rather than everyone paying everyone.
Choosing a split mode
Equally is right for a shared meal where everyone ate roughly the same, or a taxi. Any leftover cent goes to one person rather than disappearing — the parts always add back up to the exact total.
By shares is the most useful and the least used. Weights, not money: if one person stays three nights and another stays one, put 3 and 1. For rent by room size, use rough square metres. Two people in a couple sharing a room in a four-person flat? Give them 2 and everyone else 1.
By percent suits splitting by income — a common arrangement for couples where one earns more. Work out each person's share of the combined income and use those percentages. They have to total 100.
Exact amounts is for an itemised restaurant bill, where you already know what each person ordered and just want the settlement worked out.
Splitting rent fairly
Even splits are only fair when the rooms are equivalent, which they rarely are. Two approaches that hold up:
- By room size — use shares mode with approximate floor area. A 16m² room against a 10m² room is 16 and 10. Crude, but defensible, and much better than arguing.
- By income — use percent mode. If one person earns 60% of the household total, they pay 60%. Common where partners have very different salaries.
Shared bills — electricity, internet, council tax — are usually split equally even when rent isn't, since consumption doesn't scale with bedroom size.
Splitting a trip
Trips are where uneven splitting really matters, because people arrive and leave on different days and skip different activities. The practical approach is to split each expense among the people it actually applied to, rather than trying to build one grand formula for the whole trip. Accommodation by nights stayed, the rental car among whoever used it, dinner among whoever ate.
That's more bookkeeping than a single calculation, which is the point at which a shared group beats a calculator — everyone can add their own expenses as they go instead of one person reconstructing it from receipts on the flight home.
Why the cents matter
Split £100 three ways and you get £33.33 each, which is £99.99 — a penny vanishes. Do that across thirty expenses on a two-week trip and the books quietly stop balancing.
This calculator gives the spare cent to someone rather than losing it, so the parts always reconstruct the exact total. It uses the same code as our expense tracker, which is covered by tests specifically for this: whatever the amount and however many people, the shares add up.
When a calculator stops being enough
A calculator is right for one bill on one evening. Once the same people are splitting several things over days or weeks, you want a running total everyone can see — which is what Splitpond does. Create a group, share the link, and everyone can add expenses without making an account or installing anything. It's free with no cap on expenses, which is a promise we've put in writing.
Common questions
How do you split a bill with tip?
Work out the tip on the bill total, add it, then divide by the number of people. For a $120 bill with an 18% tip, the tip is $21.60, the total is $141.60, and four people pay $35.40 each. The calculator on this page does it as you type, including the tip percentage you choose.
Should you tip on the pre-tax or post-tax amount?
Either is normal, and the difference is small. Tipping on the pre-tax subtotal is the stricter reading; tipping on the total is more common because it is what the card machine offers. On a $100 bill with 10% tax, tipping 20% pre-tax is $20 and post-tax is $22 — a $2 difference split between four people is 50 cents each.
How do you split a bill when one person had more?
Use exact amounts: enter what each person actually ordered, then add tax and tip proportionally. If that feels like too much bookkeeping for one meal, splitting equally and letting it even out across the group over time is usually the friendlier answer — most groups eat together more than once.
How do you split rent fairly when the rooms are different sizes?
Two approaches hold up. By room size: use shares mode with approximate floor area, so a 16 square metre room against a 10 square metre room is 16 and 10. By income: use percent mode, so someone earning 60% of the household total pays 60% of the rent. Shared bills like electricity and internet are usually split equally regardless, since usage does not scale with bedroom size.
What happens to the leftover cent?
Splitting $100 three ways gives $33.33 each, which is $99.99 — a cent disappears. This calculator gives the spare cent to someone rather than losing it, so the shares always add back to the exact total. Across thirty expenses on a trip, that difference is what stops the books quietly drifting.