The formula
Step 1: find 10%
Move the decimal one place to the left. On a $64.50 bill, 10% = $6.45.
Step 2: build the tip you want
| Tip | Shortcut | On $64.50 |
|---|---|---|
| 20% | Double 10% | $12.90 |
| 15% | 10% + half of 10% | $6.45 + $3.23 ≈ $9.68 |
| 18% | 20% − 2% (2% = 10% ÷ 5) | $12.90 − $1.29 = $11.61 |
| 25% | Divide the bill by 4 | ≈ $16.13 |
| 10% | Move the decimal | $6.45 |
Rounding up to the nearest dollar is normal — on this bill, a $12 or $13 tip for great service is easy and generous.
Tip on the pre-tax or after-tax amount?
Etiquette guides traditionally say tip on the pre-tax subtotal, but many people tip on the total because it’s simpler. The difference is small: on a $60 subtotal with 8% tax, a 20% tip is $12.00 pre-tax vs $12.96 after tax.
The “double the tax” shortcut
In places where sales tax is close to 8–10%, doubling the tax line gives roughly a 16–20% tip. It’s a quick sanity check — but tax rates vary a lot, so don’t rely on it everywhere.
FAQ
How do I calculate a 20% tip quickly?
Find 10% by moving the decimal one place left, then double it. On $47, 10% is $4.70, so 20% is $9.40.
How much is a 15% tip on $50?
10% is $5, half of that is $2.50, so 15% is $7.50.
How much is an 18% tip on $100?
$18. On any bill, 18% is 20% minus one-tenth of that 20%.
Should I tip on a discounted or comped meal?
It’s good practice to tip on what the bill would have been before the discount, since the service was the same.
Related
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