How tip calculator Works
The pre-tax question, settled
Tipping on the pre-tax subtotal is the traditional and defensible base — the tax goes to the government, not the server. In practice the difference is small (on a $100 bill with 8% tax, $0.80 at 10%... about $1.60 at 20%), but multiplied across years of meals it is real money — and calculating on pre-tax is unambiguously fair.
What percentage, where
US sit-down service: 18–20% standard, 15% for merely fine, 22%+ for exceptional. Counter service and takeout: 0–10% is common and fine. Bartenders: $1–2 per drink or 15–20%. Delivery: 15–20% with weather and distance bonuses. The US is an outlier globally — in much of Europe and Asia, service is included and tipping stays symbolic.
The rounding trick servers notice
Rounding the total to a clean figure ($86.40 + 18% → $102) makes the tip instantly verifiable and the signature line easy. On cards, servers see the written number; on split bills, clean figures prevent the "wait, who owes what" autopsy that ruins the walk out.