Español · Português · Français · Deutsch

How to calculate a tip in your head

Every tip starts from 10%: move the decimal point one place. 15%, 18% and 20% all come from there.

10%: move the decimal point

Move the decimal point one place to the left. 10% of $48 is $4.80, and 10% of $130 is $13.

1. 10% of $48
2. $48 ÷ 10 = $4.80

Why it works: 10% is one tenth, and dividing by 10 moves every digit one place.

20%: double the 10%

Find 10%, then double it.

1. 20% of $48
2. 10% = $4.80
3. $4.80 × 2 = $9.60

Why it works: 20% is 10% twice.

15%: 10% plus half of it

Find 10%, halve it to get 5%, and add the two.

1. 15% of $48
2. 10% = $4.80
3. 5% = $2.40
4. $4.80 + $2.40 = $7.20

Why it works: 15% is 10% + 5%, and 5% is half of 10%.

18%: 20% minus a tenth of it

Find 20%, then take off a tenth of that.

1. 18% of $50
2. 20% = $10
3. 2% = $1
4. $10 − $1 = $9

Why it works: 2% is a tenth of 20%, and 20% − 2% = 18%.

Round the bill first

Tip on a round number close to the bill. On $47.60, work out 15% of $48: $7.20. Nobody needs the tip to the cent.

1. 15% of $47.60
2. ≈ 15% of $48
3. ≈ $7.20

Why it works: Rounding by 40 cents changes a 15% tip by 6 cents.

Try it

Tap a problem to check your answer.

10% tip on $36

= $3.60

15% tip on $60

= $9

20% tip on $45

= $9

5% tip on $40

= $2

More money math: Discounts · Splitting a bill · Comparing prices

In Math Daily, Perci asks problems like these: tips, discounts and splitting the bill, alongside fractions and percents.

Common questions

How much should I tip?

It depends on the country. In the US, 15% to 20% is usual at a sit-down restaurant; in much of Europe, rounding up or leaving 5% to 10% is plenty.

Do I tip on the amount before or after tax?

Both are common. The traditional rule is to tip on the total before tax.