Income-based expense splitting – how to calculate it

Income-based splitting means that whoever earns more also takes on a larger share of the shared costs – in proportion to their income. Here’s how to calculate it, step by step.

The worked example

1. Add up your incomes after tax. Alex: 28 000 kr, Sam: 35 000 kr → 63 000 kr in total.
2. Work out each person’s share. Alex: 28 000 / 63 000 ≈ 44.4%. Sam: 35 000 / 63 000 ≈ 55.6%.
3. Multiply the share by the shared expenses. With 15 000 kr in shared expenses, Alex pays 6 667 kr and Sam pays 8 333 kr.

What counts as income?

Net pay (after tax) is the most common choice, but be consistent: if you count child benefit, student aid or side income for one of you, do the same for the other. Update the shares whenever someone’s pay changes – otherwise the unfairness creeps back in.

When does this method fit?

• You earn different amounts but want it to feel equal.
• You want to keep your private finances separate from what’s shared.
• You want a rule that recalculates itself when life changes.

If your goal is instead for both of you to have exactly the same amount left in your account after the bills, take a look at the equal leftover method – we compare all three methods in the guide to splitting fairly.

In Inget tjafs the whole calculation is handled automatically: add your incomes and expenses, choose “By income” and see instantly who should pay what.