How to split expenses fairly when you earn different amounts

You move in together, you open a shared pot, and you agree to split things down the middle. It's simple, it's tidy, and for a while it feels like the fair thing to do. Then one of you gets a raise, or you realize you've quietly been earning 40% more than your partner the whole time — and the neat 50/50 starts to chafe.

The problem isn't your relationship. It's that an equal split and a fair split are not the same thing when your incomes differ. Once you can see that clearly, the fix is just a little arithmetic.

Why 50/50 stops feeling fair

Imagine two partners. Alex takes home €4,000 a month; Jordan takes home €2,800. Their shared costs — rent, groceries, utilities, the streaming pile — come to €2,400 a month.

Split 50/50, each pays €1,200. Sounds fair. But look at what that €1,200 costs each of them relative to what they earn:

Same euros, very different weight. Jordan hands over 43% of everything they earn while Alex parts with 30% and keeps a much larger cushion. Month after month, that gap is what turns "we split everything equally" into a low, persistent hum of resentment.

Three ways couples actually split

There's no single correct answer — only trade-offs. Most couples land on one of these three:

If your incomes are within a few percent of each other, honestly — keep 50/50. It's not worth the overhead. The proportional method earns its keep the moment there's a real gap.

The income-proportional formula

It's one line. Each partner's fair share of a shared cost is:

your income ÷ combined income × the shared cost

Back to Alex and Jordan. Their combined income is €4,000 + €2,800 = €6,800. So:

• Alex's share: 4,000 ÷ 6,800 = 58.8%
• Jordan's share: 2,800 ÷ 6,800 = 41.2%

Apply those percentages to the €2,400 of shared costs and the picture changes:

That's the quiet magic of the proportional method: both partners now contribute the exact same percentage of their income — 35.3% each. The euro amounts are different, but the sacrifice is identical. Nobody's cushion gets crushed.

Where it gets messy (and what to do)

The formula is easy. Real life is less tidy. A few common snags:

Irregular or freelance income

If one of you has a bumpy income, don't recompute your percentages every month — you'll go mad. Pick a sensible average (say, a rolling three-month or annual figure) and revisit it a couple of times a year, not weekly.

One-off big purchases

A new sofa or a flight home isn't a monthly bill. Decide up front whether large one-offs follow the same proportional split or get handled case by case. Most couples apply the same ratio — it's the fairest default and saves a negotiation each time.

Shared vs. personal

Proportional splitting is for shared life — the roof, the food, the bills you both rely on. Your own gym membership, your hobbies, your gifts to each other stay yours. Keeping that line bright is what makes the shared pot feel clean rather than surveilled.

What counts as "income"?

Use take-home (after-tax) pay, not gross — it's the money that actually funds the household. If one of you has significant non-salary income, fold it in. The goal is that "combined income" reflects real capacity to contribute.

Keep it low-friction

Here's the thing nobody tells you: the method is the easy part. The reason most couples drift back to a lazy 50/50 (or to one person silently covering everything) isn't that proportional splitting is hard — it's that doing it by hand, every month, across a dozen expenses, is a chore.

So automate the boring bit. Enter your two incomes once, tag what's shared, and let a tool weight every expense for you. When the split is calculated the same way every time and both partners can see it, the fairness stops being a monthly conversation and just becomes… how your household works.

That's exactly what Monio was built to do: you set the incomes, mark what you share, and it keeps the split fair and visible — 50/50, income-weighted, or a custom share per expense — so month-end is a number you both already trust.