How to · Math
How to split a bill with tax and tip
Tax and tip should be split the same way the food and drinks are split — proportionally. If you ordered 25% of the subtotal, you owe 25% of the tax and 25% of the tip. Anything else means somebody at the table is paying for somebody else's order.
Short answer
Each person's share of tax and tip equals their share of the subtotal. Subtotal share × tax = tax share. Subtotal share × tip = tip share.
Step-by-step
- 1
Add up the group subtotal
This is the bill before tax and tip — just the food and drinks. Tax and tip will be split based on this number.
- 2
Find each person's share of the subtotal
Divide each person's items total by the group subtotal. That gives you their percentage of the bill (e.g., 0.25 for 25%).
- 3
Apply that percentage to tax and tip
Multiply the tax by each person's percentage. Multiply the tip by the same percentage. Add both onto their subtotal for the final amount they owe.
- 4
Cross-check the total
Add everyone's final amounts together. The sum should match the receipt total. If you're off by a few cents, it's rounding — add the difference to the largest share.
A worked example
Subtotal is $100. Tax is $8.25 and tip is $20. Total is $128.25. Pat ordered $40, Riley ordered $35, Sam ordered $25. Pat's share: 40% × ($8.25 + $20) = $11.30, plus $40 = $51.30. Riley: 35% × $28.25 = $9.89, plus $35 = $44.89. Sam: 25% × $28.25 = $7.06, plus $25 = $32.06. Totals to $128.25.
Common pitfalls
- Tipping a percentage of the post-tax total without saying so — that's a hidden bump on everyone's share.
- Splitting the tip evenly while splitting the food unevenly — the math stops adding up to the receipt total.
- Calculating tax-and-tip on the original menu price after a discount or coupon — discounts should reduce the subtotal first.
- Rounding each person up to the nearest dollar — you can over-collect $3-5 across a six-person table.
Let SplitterBot® handle the math
SplitterBot does the proportional math from the receipt automatically. You assign items to people, and tax, tip, and fees split themselves to the cent.
FAQ
Should I tip on the pre-tax or post-tax amount?
Either is defensible. Tipping on the post-tax total is a few percent more generous. The important part for a group is that everyone agrees, because the choice changes each person's share.
How do I split a service charge?
A service charge is built into the bill and behaves like tax — split it proportionally to each person's subtotal. If there's also a regular tip on top, split that proportionally too.
What if the tip is a flat dollar amount?
Same approach. Each person's share of the flat tip equals their share of the subtotal. A $20 tip on a $100 subtotal where you ordered 30% means you pay $6 of the tip.
More how-to guides
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