The oldest calculator problem, still useful: quickly work out a tip and split the bill without doing arithmetic in front of the waiter or your friends.
The Math
Tip = Bill × Tip % Total = Bill + Tip Per Person = Total ÷ People
Worked Example
An $85 bill at 18% tip split 4 ways: tip is $15.30, total is $100.30, and each person owes $25.08.
Frequently Asked Questions
What percentage should I tip?
U.S. norms are 18–20% for standard restaurant service; higher for exceptional service. Norms vary widely by country and industry.
Tip on pre-tax or post-tax?
Traditionally pre-tax, but tipping on the full amount including tax is common and considered acceptable.
Delivery and takeout?
Delivery typically 10–15% or a $3–5 minimum. Takeout tipping is optional — often 10% for good service or nothing.