Guides/Tip mental math
How to calculate tip without a calculator
Phone dead, receipt in hand, and the waiter is waiting? A few percentage shortcuts get you close enough for a fair tip — then round to a convenient dollar amount.
The 10% anchor
Move the decimal point one place left: $86.40 → $8.64 is about 10%. Everything else builds from there.
- 20% = double the 10% amount ($8.64 × 2 ≈ $17.28)
- 15% = 10% + half of 10% ($8.64 + $4.32 ≈ $12.96)
- 5% = half of 10% ($4.32)
- 18% ≈ 20% − 2% (2% ≈ one-fifth of 10%) → $17.28 − $1.73 ≈ $15.55
- 25% = 20% + 5%, or quarter of the bill
Worked table examples
- $40 bill, 20%: 10% = $4 → tip $8 → total $48.
- $55 bill, 15%: 10% = $5.50; half = $2.75 → tip ≈ $8.25(round to $8 or $9).
- $86.40, 18%: 10% ≈ $8.64; 20% ≈ $17.28; subtract ~$1.73 → tip ≈$15.55.
- Split three ways: after tipping, divide the grand total by 3. $101.95 ÷ 3 ≈ $34 each.
Rounding tips
Round the tip up to the next dollar if you want a clean total. For large parties, confirm whether the restaurant already added a service charge before doubling up.
Common mistakes
- Tipping only on the cash portion when the rest was paid by card (staff usually pool tips).
- Forgetting a printed service charge already on the bill.
- Splitting the food evenly but forgetting to include tip in each person’s share.
When to use the calculator instead
For exact cents, custom tip %, or many people, use the freeTip Calculator. For customs and % ranges, readhow much to tip.