Couples bill split calculator: income-based vs 50/50

Paying $750 each takes a different share of a $3,000 income than a $2,000 income. Compare both approaches with your numbers before agreeing on how to split your bills.

How to split bills proportionally to income

Divide each person’s income by your combined income, then multiply that share by your common expenses.

Contribution = shared expenses × individual income ÷ combined income.

Use take-home income after tax and expenses from the same period, here one month. Include only costs you have agreed to share, such as rent, groceries, electricity or a shared subscription. Keep personal expenses separate.

An example with incomes of $3,000 and $2,000

In this illustrative example, rent is $1,000, groceries are $350 and other bills are $150. Shared expenses total $1,500, against a combined monthly income of $5,000.

• Income-based split: person 1 earns 60% of the combined income and contributes $900. Person 2 earns 40% and contributes $600. Each uses 30% of their income for shared bills.
• 50/50 split: each contributes $750. That uses 25% of the first person’s income and 37.5% of the second person’s income.

The proportional split leaves $2,100 and $1,400 respectively after shared expenses. The equal split leaves $2,250 and $1,250. These amounts are before personal expenses, debts and savings. They are not bank account balances.

The calculation does not decide your agreement

An income-based split gives each person the same percentage burden, apart from rounding. It does not leave both people with the same amount. A 50/50 split makes the contributions equal, even when incomes differ.

Neither method accounts for housework, childcare or personal commitments. Agree on which expenses to share and review the arrangement when your circumstances change. MoneyHelper’s guide to managing money as a couple also recommends agreeing on contributions and reviewing them when things change.

Variable income, zero income and rounding

What if someone’s income changes each month?

You can use that month’s income or agree on an average over several months. Use the same period for both people and decide when to review the amounts. The calculator compares the numbers entered; it does not predict future earnings.

What if one person has no income?

The proportional split assigns them zero and the other person covers the entire total. That mathematical result does not establish whether the budget is affordable. With two zero incomes, a proportional split is undefined. The calculator still shows 50/50 and flags negative remaining amounts.

Why might the contributions differ by one cent?

$100.01 cannot be split into two identical amounts to the cent. The calculator keeps the total intact: $50.01 and $50.00. For an income-based split, leftover cents go to the largest calculation remainders, with person 1 taking priority in a tie.

Once you agree on shares, record who paid

A planned contribution does not tell you who owes whom. If you agree on 60/40 and person 1 pays $1,000 in rent, the shares are $600 and $400. Person 2 owes them $400 for that bill, before other payments and reimbursements.

With Spliz for couples, record the expense, who paid and the exact shares you agreed on. The app updates your balances. This calculator does not send shares to the app or set up a recurring rule. The copy button includes contributions without your incomes.

For a trip together, our travel budget template also helps compare planned and actual costs.

Sources and method

• MoneyHelper, managing money jointly or separately, on agreeing which bills to share and how to contribute. Accessed October 14, 2026.
• Illustrative examples, reproducible using the formula above. Calculations run locally to the cent, without currency conversion or payments.