Your phone dies. The bill arrives. The table is waiting. Can you calculate 20% of $73 in your head without reaching for an app? Yes — easily. Here are the mental math shortcuts that make tipping calculation fast, accurate, and genuinely satisfying.
Any tip calculation starts with 10% — because 10% is just moving the decimal point one place to the left. From there, everything else is simple addition.
| Tip % | How to Calculate | Example ($75 bill) |
|---|---|---|
| 10% | Move decimal left one place | $7.50 |
| 15% | 10% + half of 10% | $7.50 + $3.75 = $11.25 |
| 18% | 10% + 10% - 10%÷5 | $15.00 - $1.50 = $13.50 |
| 20% | Move decimal + double it | $7.50 × 2 = $15.00 |
| 25% | 10% × 2 + half of 10% | $15.00 + $3.75 = $18.75 |
Look at the dollar amount. Drop the last digit and double: $84 bill → $8 → $16. Done. That's your 20% tip. The dropped cents mean you're leaving roughly 19–20% which is exactly right.
Get 10% (move decimal). Then add half that number. $60 bill → $6 + $3 = $9. Done. For odd numbers: $73 bill → $7.30 + $3.65 = $10.95 ≈ $11.
Calculate 20%, then subtract 10% of that: $80 bill → 20% = $16 → subtract $1.60 → $14.40. Alternatively: double the bill, move the decimal twice left. $80 → $160 → $1.60 → $16.00 wait — that's 20%. OK: just do 20% and subtract $1–2 to get to 18%.
🧮 The easiest method of all: Round the bill to the nearest $5 or $10, calculate 20%, then round your tip to the nearest dollar. $73.40 bill → round to $75 → 20% = $15. Tip: $15. Accurate enough, fast, and satisfying.
| Bill | 15% Tip | 18% Tip | 20% Tip | 25% Tip |
|---|---|---|---|---|
| $25 | $3.75 | $4.50 | $5.00 | $6.25 |
| $50 | $7.50 | $9.00 | $10.00 | $12.50 |
| $75 | $11.25 | $13.50 | $15.00 | $18.75 |
| $100 | $15.00 | $18.00 | $20.00 | $25.00 |
| $150 | $22.50 | $27.00 | $30.00 | $37.50 |
| $200 | $30.00 | $36.00 | $40.00 | $50.00 |
Mental math is great for quick social situations. For anything more complex — split bills, adjusting for service, multi-country travel — our free calculator handles every scenario instantly. But knowing the math yourself means you're never caught off guard when your phone isn't handy.
Move the decimal point one place left to get 10%, then double it. Example: $65 bill → $6.50 (10%) → $13.00 (20%). For 15%, take 10% plus half of that: $65 → $6.50 + $3.25 = $9.75.
Either is acceptable, but tipping on the post-tax total is now the most common practice and easiest calculation since that's the number shown on the bill. The tax difference is small enough that it rarely matters in practice.
$9. To calculate: 10% of $50 = $5. 5% of $50 = $2.50. 3% of $50 = $1.50. Total: $5 + $2.50 + $1.50 = $9. Or: move the decimal ($5.00), double it ($10.00), then subtract 10% of that ($1.00) = $9.00.
Whatever the situation, our free calculator helps you tip the right amount in any country, any situation.
Try the Free Tip Calculator →Helpful resources for travelers — from booking tours to finding the perfect hotel.