Traditional rule: tip on pre-tax subtotal. Practical rule: most people tip on the total. The gap between them is small — 1–2% of the bill — and the server rarely cares. Here's the math.
The math
Bill: $100 food + $8 tax = $108 total. Tipping 20%:
- On pre-tax — 20% × $100 = $20. Total paid: $128.
- On post-tax — 20% × $108 = $21.60. Total paid: $129.60.
The $1.60 difference is 1.6% of the food bill. On bigger dinners or higher-tax areas the gap scales, but it stays small.
When it matters
Group dinners with careful splitters: pre-tax is fair and traditional. Big bills: $500 at 9% tax = $9 difference between methods. Otherwise, just tip. The server doesn't need you to pick a methodology.
The server's view
Most servers don't track whether you tipped pre-tax or post-tax. They see a dollar amount. A "good tipper" in their book is someone who hit 20% and didn't stiff. The pre/post debate is mostly a customer anxiety.
Enter the amount you want to tip on. The tool handles either pre-tax or total.