Core answer: Tipping math: tip = pre-tax bill × percentage; total = bill × (1 + rate). Quick mental anchors: 10% = move the decimal (¥236 → ¥23.6); 15% = 10% + half of that (¥23.6 + ¥11.8 = ¥35.4); 20% = double the 10% (¥47.2). In mainland China tipping is NOT customary; in the US, 15–20% at sit-down restaurants is the social contract; Japan finds tips mildly offensive.
The mental-math ladder
| Rate | Trick | On $84.00 |
|---|---|---|
| 10% | decimal shift | $8.40 |
| 15% | 10% + 5% (half of 10%) | $12.60 |
| 18% | 20% − 2% | $15.12 |
| 20% | 10% × 2 | $16.80 |
| 25% | quarter of bill | $21.00 |
Rounding strategy: compute on the pre-tax subtotal, round the TOTAL to a clean number — waiters remember generous round totals, and your statement is easier to audit.
Where tipping applies (US-centric rules)
| Venue | Expected |
|---|---|
| Sit-down restaurant | 15–20% pre-tax |
| Bar | $1–2/drink or 15–20% of tab |
| Delivery | 10–15% (min $3–5) |
| Taxi/rideshare | 10–15% |
| Hotel housekeeping | $2–5/night (daily, staff rotates) |
| Coffee counter | optional, $1 or jar change |
| Takeout counter | 0–10% (optional) |
Global cheat sheet
- China / Japan / Korea / Singapore: no tipping culture; Japan may read it as an insult — a smile and "gochisousama" is the tip.
- Europe: service included by law in most countries; rounding up 5–10% is appreciated, not required.
- US / Canada: 15–20% is effectively mandatory at table service; servers' base wage can be $2.13/h federally.
Worked examples
Example 1 — Split with tip. Dinner $236.50, 4 people, 18% tip: tip = 236.50 × 0.18 = $42.57; total $279.07 → $69.77 each. Round to $70 — done in 10 seconds with the ladder.
Example 2 — Pre-tax vs post-tax. Bill $100 + 8.875% tax = $108.88. 20% on pre-tax = $20; on post-tax = $21.78. Both circulate; pre-tax is the traditional standard.
Example 3 — Service-charge trap. "18% gratuity included for parties of 6+" — tipping 20% on top double-tips. Read the receipt's bottom lines before writing anything.
Common mistakes and myths
- Tipping on the discounted total — etiquette says tip on the PRE-discount amount when using coupons; the server did full-price work.
- Assuming China tips — mainland restaurants have no tip line; adding cash confuses staff. High-end hotel restaurants add a service charge (10–15%) automatically instead.
- Forgetting delivery fees aren't tips — the $3.99 "delivery fee" goes to the platform; the driver sees the tip field only.
- Zero-tipping bad service quietly — 10% + a calm word with the manager communicates; $0 reads as "you forgot", not feedback.
- Believing the tablet's default — point-of-sale screens suggesting 25/30/35% for counter service are anchoring; "custom" is one tap away and 15% is still fine for full table service.