How to calculate a tip (in your head or on paper).
The formula is one line. The useful part is the shortcuts: how to get 15%, 18%, 20% or 25% of any bill in a few seconds, how tax and discounts change the number, and how to split it without anyone overpaying.
Tip = bill × percentage ÷ 100. Total = bill + tip. Per person = total ÷ people.
Fastest shortcut: move the decimal one place left (10%), then double it (20%).
The formula
To calculate a tip, multiply the bill by the tip percentage and divide by 100. A 20% tip on a $45 bill is 45 × 20 ÷ 100 = $9, for a total of $54. If you want the total in one step, multiply the bill by 1 plus the percentage as a decimal: $45 × 1.20 = $54.
Four mental-math shortcuts
1. 10%, then double it for 20%
Move the decimal point one place to the left and you have 10%: $54.80 becomes $5.48. Double it for 20%: $10.96. This is the one shortcut worth memorising — almost every other percentage starts from it.
2. 15% = 10% plus half of it
Take the 10% figure and add half of it again. On $54.80: $5.48 + $2.74 = $8.22.
3. 18% = 20% minus a tenth
Work out 20%, then subtract a tenth of that number. On $114: 20% is $22.80; a tenth is $2.28; so 18% is $20.52.
4. 25% = divide by four
A quarter of the bill is 25%. On $64: $16. Halve it, then halve it again if dividing by four in your head feels awkward.
Bonus: double the sales tax
In places where sales tax is around 8–9%, doubling the tax line on the receipt gets you roughly 16–18%. In New York City (8.875%) doubling the tax gives 17.75% — close to an 18% tip. It doesn’t work where tax is low or zero, so treat it as a rough check.
Worked examples
Example 1 — $114 bill, 18%
Example 2 — $86.40 split three ways, 20%
Example 3 — Pre-tax vs. post-tax, 20%
Pre-tax, discounts and gift cards
Tax: etiquette guides say tip on the pre-tax subtotal; tipping on the after-tax total is common and accepted. Coupons, happy-hour prices and comped items: tip on what the bill would have been without the discount — the server did the same work. Gift cards and points: same rule; the tip is based on the value of the meal, not on what you paid out of pocket. Wine: on a very expensive bottle some diners tip a little less than the full percentage on the wine portion; on everyday bottles, tip the normal percentage.
Splitting the tip
Add the tip to the whole bill first, then divide. If each person calculates their own tip on their own share, rounding usually leaves the server a little short. When orders are very uneven, split by share: each person pays (their items ÷ the whole subtotal) × the total. The tip calculator does both, in whole cents, so the shares always add up to the total. For parties with an automatic gratuity already on the bill, use the auto-gratuity calculator instead.
Working backwards: what percentage did I tip?
Divide the tip by the bill and multiply by 100. A $12 tip on a $70 bill is 12 ÷ 70 × 100 = 17.1%. Rounding up to a clean total is common: paying $80 on a $66.50 bill means a $13.50 tip — about 20.3%.
Try it
Type the bill and drag the percentage — the receipt updates as you go.
Want a table instead? The printable tip chart lists 15–25% tips for bills from $10 to $300. Not sure which percentage to use? See the tipping guidelines.
FAQ
How do you calculate a tip?
Multiply the bill by the tip percentage and divide by 100. For a 20% tip on $45: 45 × 20 ÷ 100 = $9. Add it to the bill for the total ($54).
What is the easiest way to work out 20%?
Move the decimal point one place to the left to get 10%, then double it. On $64.50, 10% is $6.45, so 20% is $12.90.
How do I calculate an 18% tip?
Work out 20% and subtract a tenth of it. On $114: 20% is $22.80, a tenth of that is $2.28, so 18% is $20.52.
How do you calculate the tip percentage you left?
Divide the tip by the bill and multiply by 100. A $12 tip on a $70 bill is 12 ÷ 70 × 100 = 17.1%.
Should I calculate the tip before or after tax?
Etiquette guides say before tax, on the subtotal. Tipping on the total after tax is common too and only adds a little — about $1.28 more on an $80 meal with 8% tax at 20%.
How do I split a bill and tip between friends?
Add the tip to the whole bill first, then divide the total by the number of people. If people ordered very different amounts, split by share instead — the tip calculator has a Split by share mode for that.