When one person earns more, proportional splitting is the fairest approach: each person pays a percentage of shared expenses equal to their share of the combined income. If Person A earns £30,000 and Person B earns £70,000, Person A pays 30% of shared costs and Person B pays 70%. For in-the-moment bills like restaurants, itemised splitting by what each person ordered is usually simpler and more natural.
A flat 50/50 split sounds fair. Everyone pays the same. No one is being favoured. But when one person earns £28,000 and another earns £75,000, paying identical amounts means the lower earner is contributing a much larger slice of their disposable income to the same shared life.
Over time, this creates a quiet, compounding pressure. The lower earner says yes to things they can't really afford because saying no feels awkward. The higher earner remains unaware that anything is wrong. By the time the tension surfaces, it's usually been building for months.
Proportional splitting is the straightforward solution — and it's easier to calculate and propose than most people expect.
Why 50/50 Can Feel Unfair
The problem with equal splitting isn't the maths — it's the impact. A £500 monthly contribution to shared costs represents about 2.5% of a £75,000 salary (£6,250/month take-home). For someone earning £28,000, the same £500 is closer to 6% of their monthly take-home. The number is the same; the effect is very different.
This asymmetry often shows up in smaller decisions before it shows up in direct conflict. The lower earner opts out of the more expensive restaurant, suggests a cheaper holiday, or quietly resents the other's casual attitude towards shared costs. None of these signals are easy to read in the moment.
Proportional splitting doesn't solve all of this — but it removes the structural unfairness that causes it.
The Proportional Method: How to Calculate It
The formula is simple:
- Add both (or all) incomes together to get the household total
- Divide each person's income by the total — this gives their percentage
- Apply each person's percentage to any shared expense
Worked example: Person A earns £35,000/year. Person B earns £65,000/year. Combined income: £100,000. Person A's share: 35%. Person B's share: 65%.
Monthly rent of £1,500: Person A pays £525, Person B pays £975.
Electricity bill of £120: Person A pays £42, Person B pays £78.
Grocery shop of £80: Person A pays £28, Person B pays £52.
The calculation is the same every time — just multiply the expense by each person's percentage. You can set this up in a shared notes app or spreadsheet once and refer to it without recalculating each time.
Which Expenses Should Be Split Proportionally?
Not every shared expense needs the proportional treatment. A useful way to think about it is to separate shared living costs from in-the-moment shared purchases.
Shared living costs (apply proportional split)
Rent, utilities, internet, council tax, household supplies, shared subscriptions — these are the ongoing costs of your shared life and they're where proportional splitting has the most impact. A higher earner contributing more to rent means the lower earner can actually afford to be there without financial strain.
Restaurants and one-off meals (itemised is usually better)
For restaurant bills and takeaway, most couples and roommates find it more natural to pay for what they ordered rather than applying income percentages to a dinner. The person who had the steak and cocktails paying the same as the person who had a salad and sparkling water is the more obvious unfairness in that moment. For a full breakdown of restaurant splitting approaches, see our guide to how to split a restaurant bill fairly.
Holidays and large purchases
For shared holidays, furniture, or bigger joint purchases, decide upfront whether to apply proportional or equal. Either is fine — but agreeing before the booking prevents disagreement after. Many couples use proportional for ongoing costs but are comfortable with 50/50 for one-off treats if both can genuinely afford it.
Split restaurant bills by what each person ordered
Scan the receipt, assign items, share via link in under a minute. Free on iOS and Android.How to Have the Conversation
Bringing up unequal splitting for the first time can feel like an accusation — as if you're saying the other person has been getting a better deal. The key is to frame it as a system you're proposing, not a complaint about the past.
"I was thinking it might make more sense for us to split things proportionally to what we each earn — it tends to feel fairer for both people in the long run" is a reasonable, non-confrontational opener. It positions proportional splitting as a general principle rather than a personal demand.
The best time to have this conversation is before you establish a shared routine — when you're first moving in together, starting to share regular expenses, or reassessing an existing arrangement. Changing something mid-stream feels more like a renegotiation; establishing it at the start feels like a sensible agreement.
When 50/50 Is Actually Fine
Proportional splitting isn't necessary in every situation. If both people earn similar amounts, 50/50 is simpler and perfectly fair. If the income gap is modest and both people are comfortable, equal splitting may still feel right. And sometimes, the higher earner actively chooses to cover more as an act of generosity rather than a calculated arrangement — which is also a valid approach, as long as it's a genuine choice rather than an unspoken expectation.
The goal is a system that both people feel is fair, not a mathematically optimal formula. The proportional method is a useful starting point when 50/50 is creating strain — but the conversation matters more than the calculation.
For more on managing shared expenses between couples, see our guide to how to split bills as a couple, which covers all three main approaches in detail. For roommate situations, the same proportional logic applies — see our guide to how to split rent fairly with roommates.
Frequently Asked Questions
How do you split bills fairly when incomes are different?
The proportional method works best: add both incomes together, calculate each person's percentage of the total, and apply that percentage to shared expenses. If Person A earns £30,000 and Person B earns £70,000, Person A pays 30% of shared bills and Person B pays 70%.
Is it fair to split bills 50/50 when one person earns more?
A 50/50 split is mathematically equal but not always financially fair. When one person earns significantly more, the same absolute payment represents a much larger proportion of the lower earner's income. Proportional splitting — each person pays according to their share of combined income — is often fairer in these situations.
How do you bring up unequal bill splitting without making it awkward?
Frame it as a practical arrangement rather than a complaint. Something like "I was thinking we could split things proportionally to what we each earn — it tends to feel fairer for both people" opens the conversation neutrally. Raising it before moving in together or establishing a shared routine is easier than trying to renegotiate an existing arrangement.
Should restaurant bills also be split proportionally when incomes differ?
For restaurant bills, most couples and roommates prefer itemised splitting — each person pays for what they ordered — rather than applying income percentages to a dinner bill. SplitEven can scan a receipt and assign items per person in under a minute, which is usually the simplest and most natural approach for one-off meals.