How to Use This Tool
Enter the bill and the number of people. The shares are calculated so they add up to the total exactly, which is not what dividing and rounding gives you.
Why the parts do not add up
Money comes in whole pennies. Divide 100 by three and each share is 33.333…, which rounds to 33.33, and three of those is 99.99. The missing penny does not disappear — it was never allocated, because rounding each share independently loses a fraction from each one.
The fix is to work in pennies from the start: divide the whole amount into whole units, then hand out the remainder one penny at a time. Somebody pays a penny more than somebody else, which is unavoidable and is far better than the group being short when the card is presented.
Tip before or after tax
Both are defensible and the difference is small but real. Tipping on the pre-tax amount means you are tipping on the food and drink; tipping on the total means you are also tipping on the tax, which nobody in the restaurant received.
The gap is the tax rate multiplied by the tip rate. At 8% tax and a 20% tip that is 1.6% of the bill — on a hundred, about a pound and sixty. Small enough that it is not worth an argument, and large enough that people have them anyway. This shows both so nobody has to guess which was used.
Uneven splits
The lower box handles the more honest version: everyone pays for what they ordered, with tip and tax distributed in proportion. Someone who had a starter and two drinks pays more of the tip than someone who had a salad, which is usually what people mean by "fair" even when they say "just split it".
The same rounding rule applies, so the individual amounts still sum to the total exactly.
Rounding up
The round-up option gives every person a whole amount, which is easier to transfer and easier to remember. The excess is shown separately, since it goes to the tip rather than vanishing — rounding five people up to the nearest whole unit typically adds a couple to the tip, which is usually intended and should not be silent.
A note on splitting evenly
An even split is simpler and usually fine. It stops being fine when the difference is large — one person on tap water and another on three cocktails — and the person who ordered less rarely says anything. If you are organising, offering the itemised option unprompted costs nothing and is noticed.
