Everyday Percentages
Calculate 15%, 18% and 20% Tips Without a Calculator
Build common tip percentages from simple fractions, check the final bill and handle rounding when sharing a total.
First choose the amount you are tipping on
Mental arithmetic is useful for checking a receipt, but it cannot decide the appropriate tipping custom. These examples compare chosen rates of 15%, 18% and 20%; they do not prescribe a rate for every country or service.
Read the receipt first. Decide whether your chosen base includes tax, and check for an already included gratuity or service charge. The tip and total bill guide explains those distinctions. Here the focus is finding percentages quickly and checking rounding.
Build three rates from 10% and 1%
- 10%: divide the chosen base by 10.
- 15%: add 10% to half of 10%.
- 20%: double 10%.
- 18%: calculate 20%, then subtract 2%. Find 2% by doubling 1%, where 1% is the base divided by 100.
On a $48.00 base, 10% is $4.80 and 5% is $2.40, so 15% is $7.20. For 20%, double $4.80 to get $9.60. For 18%, subtract $0.96 (2% of $48) from $9.60, giving $8.64.
Worked totals for three bill sizes
The totals below are base plus tip only. They assume no other amount needs adding. If your base excludes tax, include the actual tax separately when settling the bill.
| Base | 15% | 18% | 20% |
|---|---|---|---|
| $48.00 | $7.20 / $55.20 | $8.64 / $56.64 | $9.60 / $57.60 |
| $62.50 | $9.38 / $71.88 | $11.25 / $73.75 | $12.50 / $75.00 |
| $125.00 | $18.75 / $143.75 | $22.50 / $147.50 | $25.00 / $150.00 |
For $62.50 at 15%, 10% is $6.25 and half of that is $3.125. Their sum is $9.375, which rounds to $9.38. Keep the intermediate precision and round the final tip once. Avoid rounding 1% before multiplying: on this bill, 1% is $0.625, and rounding it to $0.63 before finding 18% would give the wrong result.
An estimate is useful if you label it as one
For a $47.80 base at 18%, rounding the base to $50 gives an estimate of $9.00. The exact tip is $8.604, or $8.60 to cents; the base-plus-tip total is $56.40. The estimate is $0.40 higher after rounding. That may be an intentional choice, but it is not an exact 18% calculation.
A quick reasonableness test is that 18% must fall between 15% and 20% of the same positive base. If it does not, check your decimal place and whether you accidentally used different bases.
Splitting is a separate calculation
A $125 base with an 18% tip totals $147.50. Split equally between four people, the unrounded share is $36.875. Four payments of $36.88 add to $147.52. To settle exactly, two people can pay $36.88 and two $36.87. Agree who covers rounding rather than assuming rounded shares will always add up.
The Tip Calculator checks the tip and total for your chosen base and percentage. It does not automatically split a group bill or decide whether tax and service charges belong in your base.
Common questions
Can I multiply the base by 1.18?
Yes, for base plus an 18% tip: B + 0.18B = 1.18B. This does not include any tax or charge absent from B.
Is subtracting 2% from 20% a percentage decrease?
Here it means subtracting two percentage points of the same base, giving 18%. Reducing the 20% tip itself by 2% would give 19.6% of the base, a different amount.
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