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Results
ExampleSmart Split
Income-based split
| Figure | Partner A | Partner B |
|---|---|---|
| Contribution | $1,488.00 | $912.00 |
| Share of household income | 62.0% | 38.0% |
| Share of own income | 48.0% | 48.0% |
| Income remaining after shared bills | $1,612.00 | $988.00 |
Equal payments
50/50 split
| Figure | Partner A | Partner B |
|---|---|---|
| Contribution | $1,200.00 | $1,200.00 |
| Share of own income | 38.7% | 63.2% |
| Income remaining after shared bills | $1,900.00 | $700.00 |
Difference between the methods
Partner A would contribute $288.00 more per month under this split.
Partner B would contribute $288.00 less per month under this split.
$3,456.00 over 12 months if income and shared expenses stay the same.
Shared expenses stay the same under both methods: $2,400.00.
How the calculator works
- Enter both monthly take-home incomes — what actually reaches each account, using the same period and definition for both people.
- Enter the total of the monthly expenses you have agreed to share.
- Choose the currency label. It changes the symbol and the grouping only; no amount is converted.
- Press Calculate split. The results replace the example, and Reset example brings the published figures back.
To split rent alone, enter the monthly rent as the shared expense total. To split every household bill, enter their combined monthly amount instead.
The formula
Partner A share = income A ÷ (income A + income B)Partner B share = income B ÷ (income A + income B)Partner A contribution = shared expenses × Partner A sharePartner B contribution = shared expenses × Partner B shareUse take-home incomes from the same period and in the same currency, and agree first on which expenses are shared.
If both incomes are zero there is no proportion to divide by, so only the 50/50 result is shown. You can read how the income-based formula works in more detail, including a full monthly example.
Worked example
Monthly take-home incomes of $3,100.00 and $1,900.00 make a combined $5,000.00, so the household income shares are 62.0% and 38.0%. Applied to $2,400.00 of shared monthly expenses, the two methods look like this.
| Figure | Income-based | 50/50 |
|---|---|---|
| Partner A contribution | $1,488.00 | $1,200.00 |
| Partner B contribution | $912.00 | $1,200.00 |
| Partner A share of own income | 48.0% | 38.7% |
| Partner B share of own income | 48.0% | 63.2% |
| Partner A income remaining | $1,612.00 | $1,900.00 |
| Partner B income remaining | $988.00 | $700.00 |
Partner B would contribute $288.00 less per month under this split. $3,456.00 over 12 months if income and shared expenses stay the same.
The household pays $2,400.00 either way: the money moves between the two people, it is not saved. If the two columns are hard to weigh against each other, this guide can help you interpret the difference between the methods.
Rounding
Contributions are worked out in whole cents, and both methods use the same policy, so the two contributions always add up to the expense total exactly. Each person takes the whole-cent part of their exact share; the single cent that can be left over goes to the larger fractional remainder, and to Partner A on a tie.
Percentages are displayed rounded to one decimal and never feed the money calculation. Because of that rounding, two percentages that read the same can still stand for amounts that differ by a cent.
What this calculator leaves out
- Income remaining after shared bills is income minus the shared contribution shown here. It is not disposable income after all your obligations.
- It does not compute who owes whom, because it has no record of what either of you has already paid.
- It does not account for taxes, savings, debts, care work or anything else either partner contributes.
- Moving a contribution from one person to the other is a redistribution, not a household saving: the total is the same under both methods.
- Nothing you enter is stored or sent. The figures stay in this page, and reloading it restores the example.
To keep a record of what was paid and by whom, you can track shared expenses in Fairmony.
Frequently asked questions
Is this calculator free?
Yes. You can calculate a split without an account or a Fairmony subscription.
Can I use it just for rent?
Yes. Enter the monthly rent as the shared expense total. To split all household bills, enter their combined monthly amount instead.
Does the calculator save our incomes?
The calculator does not send or save your entries. They are used in this page to calculate the result. Reloading the page restores the example.
Can we enter different currencies?
Use the same currency for both incomes and the expense total. Changing the currency label does not convert amounts.
Does “income remaining” include personal bills?
No. It is income minus the shared contribution shown here. It does not subtract personal expenses, debt payments or savings.
Track this split in Fairmony
Use Fairmony to track shared expenses with an income-based split. Your calculator entries are not transferred to the app.
