Understanding tipping
A custom, not a calculation.
The math is trivial. The norms are everything.
The math.
Tip is bill × percent ÷ 100. Total is bill plus tip. If you're splitting, divide the total by the number of people. That's all the calculation has to teach. Everything interesting about tipping is cultural.
tip = bill × pct ÷ 100
Tip on pre-tax or post-tax?
The traditional rule in the United States is to tip on the pre-tax bill — sales tax goes to the state, not the server. In practice many people tip on the post-tax total because it's the number on the bottom of the receipt; the difference is a percent or two. Both are accepted.
Country norms.
A short tour
- United States — 18–22% expected, often required by living wage
- United Kingdom — 10–12.5% (often added as service charge)
- Continental Europe — 5–10% if service was good
- Japan, South Korea — no tipping; can be considered insulting
- Australia, NZ — no tipping; staff are paid full minimum wage
Service charge vs tip.
A "service charge" added by the restaurant is technically a fee that may or may not reach the staff — that depends on local labour law and the restaurant's policy. A tip, by contrast, is voluntary and (in most jurisdictions) goes directly to the worker. If the bill already has a service charge, tipping again is a courtesy, not an expectation.
Splitting evenly vs by item.
Splitting evenly is the social default and what this tool computes. Splitting by item is fairer when courses and drinks vary widely — most modern POS systems can do it, and it's polite to ask the server when ordering rather than at the end.