The formula
Tip = bill × tip percentage ÷ 100. On an $86.40 bill, an 18% tip is 86.40 × 0.18 = $15.55, for a total of $101.95.
Doing it in your head
- 10%: move the decimal point one place left. $86.40 → $8.64.
- 20%: double the 10% figure. $8.64 × 2 = $17.28.
- 15%: the 10% figure plus half of it. $8.64 + $4.32 = $12.96.
- 18%: 20% minus a tenth of the 20% figure. $17.28 − $1.73 = $15.55.
Round the bill to a friendly number first if you only need a rough figure: $86.40 is close to $86 or $90.
Splitting the bill
Add the tip to the bill, then divide by the number of people. $101.95 between three is $33.98 each. People usually round up, so $34 each makes the total $102 and the tip a little higher.
The Tip Calculator does the tip, the split and the rounding up at once. For any other percentage question, use the Percentage Calculator.