Fair split calculator
Enter your net incomes and your shared fixed costs and see right away who should transfer how much to whom.
Your input never leaves your browser and is never stored.
net per month
net per month
Shared fixed costs
Fixed costs per month, total
Who currently pays how much?
Person B transfers €500 to Person A every month
How it should be
How it is now
Person A
- Target share
- €1,000
- Currently pays
- €1,500
- Difference
- €500
- Left of income
- €2,000
- Share of income
- 33%
Person B
- Target share
- €1,000
- Currently pays
- €500
- Difference
- -€500
- Left of income
- €1,000
- Share of income
- 50%
All three methods compared
| Method | Who transfers whom |
|---|---|
| 50/50 | Person B → Person A: €500 |
| By income | Person B → Person A: €300 |
| Custom share (50%) | Person B → Person A: €500 |
Work with the real due dates
Halfway through the year? Then what matters is which costs are actually still due before December. MonoBudget calculates with the real due dates of your fixed costs, spreads the adjustment evenly across the remaining months, and shows a preview for next year. The app enters the adjustment in your budget; you make the transfer yourselves, most easily as a recurring bank transfer. MonoBudget is free. Fair Split is part of Pro: a one-time purchase, no subscription.
The three methods
50/50 splits the costs exactly in half. By income sets each share based on what each person earns net: whoever earns more pays more. With a custom share you set the percentage yourselves, for example if you've agreed on 60 to 40. All three methods take the same inputs, only the target split differs. You can switch between them without re-entering the numbers, and see the differences right away in the comparison table under the result. An example: Lena earns 3,000 € net, Max earns 2,000 €. Your shared fixed costs come to 2,000 € a month, and Lena currently pays 1,500 € of it. At 50/50, each person should carry 1,000 €, so Max transfers 500 € to Lena. By income, the ratio is 3 to 2, Lena carries 1,200 €, Max 800 €, and Max transfers 300 € to Lena.
What counts as a shared fixed cost?
This covers rent or mortgage payments, service charges, electricity, heating, internet and insurance policies you took out together. Bills that come only once a year count too; the calculator spreads them across the months. Costs for children you have together, such as daycare, belong here if you want to carry them jointly. What concerns only one person stays out: a personal car, a personal phone contract, private subscriptions. Each person pays those from their own money.
Yearly and quarterly bills
Some costs do not come every month, car insurance for example once a year. The calculator turns such amounts into a monthly figure, so a yearly bill of 1,200 € counts as 100 € a month. For the split, that is fair. Your account still sees the whole bill at once, though. So put the monthly share aside, ideally in a separate sub-account, and the month the bill is due is no problem.
What changes with parental leave or part-time work?
When one person goes on parental leave (Karenz in Austria, Elternzeit in Germany) or works fewer hours, their net income often drops noticeably. If you split by income, their share of the fixed costs drops with it once you enter the new numbers. The calculator saves nothing, so re-enter the values after any bigger change. If one person has no income for a while, the by-income method falls back to 50/50, because no ratio can be formed without two incomes. During that time a custom share you agree on together usually fits better. If you want to plan the split for the rest of the year with real due dates, without retyping everything each time, that is what MonoBudget does.
Common questions
Gross or net?
Net. The calculator compares what actually lands in your account, not what's printed on the payslip.
How often should you recalculate?
Every time income or rent changes, and at least once a year even if nothing seems to have changed.
One person earns a lot more, what now?
Then splitting by income usually fits. Both carry the same percentage of their income: whoever earns less pays fewer euros, but the same share.
When is a custom share better than by income?
When you've agreed on a fixed ratio for other reasons, for example because one person also takes on unpaid care work that doesn't show up in either income.