How to Calculate Who Owes What in a Group
The math behind group expense splitting — from simple even splits to per-item proportional calculations. Including the formula and the fastest way to do it.
Before you can send a payment request, you need to know the number. Here's how to calculate each person's share — and how to skip the math entirely.
The Even Split Formula
Per person = Total bill ÷ Number of people
Example: $120 bill with 4 people = $30 per person. Add tip first: $120 + 20% tip = $144 ÷ 4 = $36 per person.
- Include tax before dividing (it's already in the total on the receipt)
- Add tip as a percentage of the pre-tax subtotal, then divide the full amount
- Round to the nearest cent — the person who organized pays or receives the rounding difference
The Per-Item Formula (Fairest)
Each person's share = their items subtotal + proportional tax + proportional tip
- Step 1: Add up each person's individual items
- Step 2: Calculate their percentage of the table subtotal (their items ÷ total food)
- Step 3: Multiply that percentage by the total tax → their tax share
- Step 4: Multiply that percentage by the total tip → their tip share
- Step 5: Add all three: items + tax share + tip share = their total
Example: You ordered $30 of a $100 food total (30%). Tax is $8 → your share = $2.40. Tip is $18 → your share = $5.40. Your total = $30 + $2.40 + $5.40 = $37.80.
How to Calculate for Shared Items
For shared items (appetizers, bottles of wine, desserts), divide the item's cost evenly among the people who shared it, then add it to each person's subtotal before calculating their tax and tip share.
Multi-Expense Reconciliation (Trips, Roommates)
For groups with multiple expenses over time: track each expense separately (who paid, how much, who it was split between). At the end, sum each person's total share across all expenses, subtract what they paid, and the difference is what they owe or are owed.
Skip the Math: Use Payback
Payback does every calculation above automatically. Scan the receipt, tap to assign items, and Payback computes each person's share including proportional tax and tip. Group Text Blast sends the results to everyone via Venmo or CashApp. Total time: under 2 minutes.
Quick Reference
- Even split: Total ÷ people (add tip first)
- Per-item: each person's subtotal + (their % × tax) + (their % × tip)
- Shared items: item cost ÷ sharers, added to each person's subtotal
- Multi-expense: sum each person's shares, subtract what they paid, net = owed/owe