Free couple expense calculator
Compare 50/50, Income-Based, and Equal-Leftover Expense Splits
Enter both partners’ monthly take-home income and your shared monthly costs. See, side by side, what 50/50, income-proportional, equal-leftover, and your own custom split would ask each person to contribute—and how much each person would have left.
No method is automatically the fairest. A 50/50 split equalizes the dollar contribution. An income-proportional split equalizes the percentage of take-home income contributed. An equal-leftover split aims to leave both partners with the same amount after shared costs and any adjustments they both agreed to include.
The calculator makes the trade-offs visible so you can choose together. It does not choose for you.
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Free tool from You Owe Me, the iPhone app for keeping shared expenses and running balances clear over time.
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Compare the methods with your numbers
Start with monthly take-home income and the shared costs you already agree belong in the calculation. You can get a useful comparison with only three numbers.
Your figures are calculated in this browser. No account is required.
Contribution comparison
What each method would mean
The same shared cost can create very different contribution amounts, income pressure, and money left. Compare all of those outcomes before selecting a working method.
Method framework
What each method is designed to equalize
Each method answers a different version of “equal.” The formula can show the result, but it cannot decide which goal fits your relationship.
| Method | What it equalizes | How it is calculated | Keep in mind |
|---|---|---|---|
| 50/50 | The dollar contribution | Shared monthly cost ÷ 2 | The same dollar amount can use very different percentages of each partner’s income. |
| Income-proportional | The percentage of take-home income contributed | Shared monthly cost × one partner’s income ÷ combined income | It does not decide whether personal obligations, unpaid work, or other non-cash contributions should affect the agreement. |
| Equal-leftover | The money remaining after shared costs and agreed adjustments | The contributions are solved so both remaining amounts would match. | It can be impossible through non-negative shared-cost contributions alone. It is a mathematical model, not a fairness verdict. |
| Custom | Whatever principle your agreed percentages represent | Shared monthly cost × each agreed percentage | The value comes from a clear agreement and review point, not from the formula itself. |
Decision framework
Choose together, not by score
The numbers can clarify the consequences. They cannot decide which personal commitments should count, how unpaid care should be valued, or what arrangement feels sustainable and safe for both people.
Before choosing a working method, ask:
- What are we trying to make equal: dollars contributed, percentage of income, money left, or something else?
- Which costs do we both agree are shared?
- Can each person meet the contribution without losing access to necessities or independent money?
- What change should trigger a review—income, rent, caregiving, health, or another major shift?
Practical note
Save a working agreement
Copy the full comparison while you are still deciding, or select a working method and save a short record of what you agreed. This is a practical note, not a legal contract.
Optional. Choose a date to revisit the method.
Optional. Add a change that should prompt a new conversation.
Select a working method to copy a chosen-method summary.
Next stage
When this calculator is enough
This calculator may be all you need when you are choosing a stable monthly rule, the shared-cost total is easy to understand, and both partners can follow the agreement without keeping a running balance.
Use the balance calculator after payments happen
A contribution rule describes what each person is expected to cover. Real spending can still be uneven: one partner may pay rent, the other may pay groceries, and transfers may happen later. Use the Couple Shared Expense Balance Calculator to compare actual payments with the rule you chose.
Apply the rule to actual expensesWorked examples
Two examples
The methods can look similar when incomes are close and very different when incomes are far apart. These examples use no agreed adjustments.
Similar incomes: the methods stay relatively close
Alex brings home $4,200 a month, Sam brings home $3,800, and their shared monthly costs are $2,000.
| Method | Alex | Sam |
|---|---|---|
| 50/50 | Contributes: $1,000 Share of income: 23.8% Has left: $3,200 | Contributes: $1,000 Share of income: 26.3% Has left: $2,800 |
| Income-proportional | Contributes: $1,050 Share of income: 25.0% Has left: $3,150 | Contributes: $950 Share of income: 25.0% Has left: $2,850 |
| Equal-leftover | Contributes: $1,200 Share of income: 28.6% Has left: $3,000 | Contributes: $800 Share of income: 21.1% Has left: $3,000 |
The methods do not produce the same result, but the differences are relatively contained. The useful question is still which outcome the couple wants their rule to equalize.
Different incomes: equal-leftover may not be feasible
Alex brings home $6,000 a month, Sam brings home $2,500, and their shared monthly costs are $3,000.
| Method | Alex | Sam |
|---|---|---|
| 50/50 | Contributes: $1,500 Share of income: 25.0% Has left: $4,500 | Contributes: $1,500 Share of income: 60.0% Has left: $1,000 |
| Income-proportional | Contributes: $2,117.65 Share of income: 35.3% Has left: $3,882.35 | Contributes: $882.35 Share of income: 35.3% Has left: $1,617.65 |
| Equal-leftover | Status: Not feasible under these inputs | |
Equal-leftover would require Alex to contribute $3,250 and Sam to contribute -$250. Because a shared-cost contribution cannot be negative, the calculator must mark this method as not feasible. Even if Alex covers all $3,000 and Sam contributes $0, they would still have $3,000 and $2,500 left.
An infeasible result is useful information. It shows that equal remaining money cannot always be produced only by changing who contributes to the shared cost.
FAQ
Frequently asked questions
Should we use gross income or take-home income?
Use monthly take-home income: the amount each person actually receives after tax and payroll deductions. Use the same definition and time period for both partners. If income varies, agree on an average or another repeatable number and record what period you used.
What does equal-leftover mean?
Equal-leftover sets the shared-cost contributions so both partners would have the same amount remaining after shared costs and any adjustments they both agreed to include. It is a mathematical model, not a judgment about what is fair.
Do personal debts or other obligations have to count?
No. The adjustment fields are optional. Include an amount only when both partners agree that it belongs in this comparison. The calculator cannot decide which personal commitments are more important or legitimate.
What if one partner has no income?
You can enter 0 as take-home income. A 50/50 or custom result can still be calculated, but the percentage-of-income figure may be undefined when a person has no income. Income-proportional will assign the shared cost according to the incomes entered. Equal-leftover may be infeasible, depending on the shared cost and included adjustments.
Is 50/50 unfair when incomes are different?
The calculator does not label 50/50 fair or unfair. It shows that 50/50 equalizes the dollar contribution, while the same amount may use a different percentage of each person’s income. The couple still has to decide which principle they want the arrangement to follow.
When should we compare the methods again?
Review the method when an income changes meaningfully, shared costs rise or fall, caregiving or work circumstances change, or the current arrangement stops feeling sustainable to either partner.
Does the calculator save or send our income?
The calculation runs in your browser. No account is required, and the income, expense, adjustment, name, and percentage values entered in the calculator must not be sent through page analytics.
Is this financial, tax, legal, or relationship advice?
No. This is an educational comparison tool. It does not provide financial planning, tax, legal, lending, debt, benefits, accounting, or relationship advice, and it does not create an enforceable agreement.