Tip and total in one step
The tip is the bill multiplied by the percentage: 15 percent of 80 is 12, so the total is 92. The calculator shows the tip and the total for the preset percentages side by side, so you can compare 15, 18 and 20 percent at a glance. Customs differ a lot between countries: in some places a service charge is already on the bill, in others 15 to 20 percent is expected, and in some a small round-up is enough. Check the bill before adding a tip.
Amounts have no currency symbol, so the calculator works the same for any currency. It counts in hundredths internally, so there are no rounding errors such as 30.000000004.
Splitting fairly
When the total does not divide evenly, the leftover cents go to some people so that the shares always add up to the total: 100 split three ways is 33.34, 33.33 and 33.33. Rounding each share up to a whole number makes paying in cash easy, and the extra simply becomes part of the tip; the calculator shows the real tip percentage after rounding.
With shares, each person gets a weight. Someone who ordered twice as much can have 2 shares, a child half a share. The bill and the tip are divided in proportion, and the table shows each person's amount and how much of it is tip.