How to split costs when you earn different amounts

Why 50/50 stops feeling equal

An equal split is the obvious starting point and, for a long time, a perfectly good one. It needs no disclosure, no spreadsheet and no conversation about money, which are three real advantages. It stays comfortable while your incomes are broadly similar, and it starts to chafe at roughly the moment they are not.

The reason is not that one person is being unreasonable. It is that an equal split makes the amount equal and leaves the effect unequal. Suppose the two of you have £3,000 and £2,000 a month after tax, and the shared costs — rent, energy, water, broadband, council tax, the weekly food shop — come to £2,000 a month.

Same bill, same flat, same fridge. Sam is spending half of everything earned on shared living and Robin a third, and Robin finishes the month with twice as much spare money. Nothing about that is anyone's fault, and no method below is morally superior to another — they simply hold different things equal. Decide which thing you want to be equal and the arithmetic follows.

One practical note before the methods: use take-home pay throughout, because that is the money that can actually pay a bill. If your income varies, average the last three or six months. And settle in advance what counts — bonuses, overtime, benefits, freelance work on the side — because the definition is the part that causes arguments later, not the division.

The three methods, in one table

Every method here divides the same £2,000 of shared costs between the same two incomes. Only the rule changes.

Notice how far apart the answers are at a 3:2 income gap, and that all three columns still add to £2,000. The sections below show where each figure comes from.

Method one: the straight equal split

Add up the shared costs and divide by the number of people. £2,000 ÷ 2 = £1,000 each. That is the whole method, and its virtues are real: it is instantly verifiable, it needs nobody to disclose a payslip, and it does not have to be recalculated when someone gets a rise.

It is the right choice more often than the internet suggests. Keep it when your incomes are close; when both of you comfortably cover your half; when you deliberately keep finances separate and both prefer the symmetry; or when the shared pot is small enough that the difference is a few pounds a month rather than a few hundred.

Stop using it when the lower earner is running out of money before payday while the higher earner is saving, when one of you has started quietly resenting a bill, or when "we can't afford that" and "we can easily afford that" are both true of the same couple at the same time. That is the signal, and it is worth acting on while it is still a mild irritation.

A halfway house that costs nothing: keep the equal split for everyday costs, and let whoever earns more absorb the occasional lumpy item — the flights, the new mattress, the vet bill — by agreement each time. It is less tidy than a formula and it works for a lot of couples.

Method two: in proportion to income

Here the thing held equal is the bite: you both pay the same percentage of your own take-home pay. Three steps.

With £3,000 and £2,000, the total is £5,000, so Robin's weight is 3,000 ÷ 5,000 = 60% and Sam's is 2,000 ÷ 5,000 = 40%. Applied to £2,000 of shared costs:

• Robin: £2,000 × 60% = £1,200, which is 40% of Robin's £3,000.
• Sam: £2,000 × 40% = £800, which is 40% of Sam's £2,000.
• £1,200 + £800 = £2,000, and both are paying the same 40% of their pay.

That last line is the whole appeal, and it is not a coincidence: the shared costs as a fraction of joint income (£2,000 ÷ £5,000 = 40%) is exactly the percentage each person ends up paying. So you can work the method backwards as a sanity check — if the shared costs are 40% of what the two of you bring in, an income-proportional split has you both spending 40% of your own pay on them.

Real incomes are not round, so expect pennies. With £3,150 and £2,050 the total is £5,200, and Robin's share is £2,000 × 3,150 ÷ 5,200 = £1,211.538…, which rounds to £1,211.54. Rather than rounding the second share independently and risking a total of £2,000.01, set it to the remainder: £2,000 − £1,211.54 = £788.46. Round every share but one; make the last one the total minus the rest. The same rounding rule, applied to three or more people, is set out in our guide to splitting rent unevenly.

The variant worth knowing about is a personal allowance floor. Strict proportionality assumes every pound of income is equally spare, which it is not: the first few hundred pounds of anyone's pay goes on things that do not scale. So give each person a fixed allowance first — say £800 — and split in proportion to what is left. The weights become £2,200 and £1,200, a total of £3,400, and the shares become £2,000 × 2,200 ÷ 3,400 = £1,294.12 and the remainder, £705.88. The floor pushes about £94 a month from the lower earner to the higher one; a bigger floor pushes more. It is a dial, and it is a reasonable one to turn.

If you want the percentages worked out for you, the income method in our rent split calculator does exactly this arithmetic in your browser and hands out the leftover pennies so the shares add to the total; the bill split calculator is the quicker option for a single shared bill.

Method three: equal leftover

This one is talked about far less than the other two and is worth understanding properly, because it is the method people reach for when they say "we should both have the same amount of spending money". What it holds equal is what is in your pocket after the shared costs are paid.

Work it out in three steps. Add both incomes. Subtract the shared costs. Divide what is left by two — that is the amount each of you keeps — and then each person pays whatever is needed to get down to it.

With £3,000 and £2,000 of income and £2,000 of shared costs: joint income is £5,000, so what remains after the costs is £3,000, and each person keeps £1,500.

• Robin pays £3,000 − £1,500 = £1,500.
• Sam pays £2,000 − £1,500 = £500.
• £1,500 + £500 = £2,000, and both are left with £1,500.

That is a 75/25 split of the costs from a 60/40 split of income, which is the first thing to notice about this method: it is much more aggressive than proportionality, and it gets more aggressive fast. The reason is visible in the formula — the amount each person keeps is fixed by the couple's joint finances, so the entire income gap lands on the higher earner's contribution. Every extra pound Robin earns increases Robin's share by fifty pence and reduces Sam's by fifty pence.

Push the gap wider and it does something that surprises people. Same £2,000 of costs, but now Robin takes home £4,500 and Sam £1,500:

Robin's share is £2,500 — more than the shared costs come to — and Sam's is negative £500. In plain terms the rule says Robin pays all £2,000 of the shared costs and hands Sam £500 on top, because that is the only way two people with £6,000 between them and £2,000 of bills both end up with £2,000 each. The maths is not broken; it is telling you honestly what "the same amount left over" implies at that income gap.

The tipping point is easy to spot. The lower earner's share hits exactly zero when their income equals half of the money remaining after costs. At £4,000 and £2,000 of income with £2,000 of costs, the remainder is £4,000, each keeps £2,000 — and Sam's whole £2,000 income is already that amount, so Sam pays nothing and Robin pays the lot. Below that, it goes negative.

So use equal leftover with your eyes open. It suits couples who genuinely pool their finances and think of the money as jointly owned, and it is the natural rule when one person is between jobs, on parental leave or studying. It suits people who keep finances separate much less well, and a transfer from one partner to the other is a different thing from sharing a bill, however neatly the formula produces it. Two common guards: cap it, by agreeing nobody's share goes below zero (or below some floor like £100, so both people are contributing something), or blend it, by taking the midpoint between the proportional and equal-leftover answers — for Robin and Sam that is (£1,200 + £1,500) ÷ 2 = £1,350 and £650.

It generalises past two people, which makes it usable in a shared house where earnings differ a lot: divide the money remaining after costs by the number of people, and each pays their income minus that. With take-home pay of £3,000, £2,600 and £2,200 — £7,800 in total — and £2,400 of shared costs, £5,400 remains, so each keeps £1,800 and the shares are £1,200, £800 and £400. They add to £2,400. Between housemates rather than partners this is a hard sell, and the milder methods in splitting rent and bills with housemates are usually the better fit.

The variants people actually use

Few couples apply one rule to everything. The arrangements that survive contact with real life tend to be hybrids, and the good news is that hybrids are just as easy to check — the shares still have to add up to the costs.

Rent by income, bills equally

The most popular hybrid, because rent is the big fixed number and the bills are small and variable. With rent at £1,400 and other shared costs at £600, Robin and Sam split the rent 60/40 — £840 and £560 — and the £600 equally at £300 each. Robin pays £1,140, Sam £860. That is gentler than the £1,200 / £800 of a fully proportional split and much gentler than equal leftover, and it keeps the fiddly monthly bills on a rule nobody has to recompute.

A flat contribution to a joint pot

Instead of splitting each expense, you each pay a fixed amount into a joint account on payday and everything shared comes out of it. Robin puts in £1,350 and Sam £750: £2,100 against £2,000 of typical costs, so £100 a month accumulates as a buffer for the quarterly and annual bills. It is the lowest-admin option by a wide margin, and its one requirement is that you look at the balance every few months and adjust the two contributions before the buffer runs dry or grows silly.

Keeping some categories personal

Draw a line between shared and personal, and split only what is over the line. Rent, energy, water, broadband, council tax, insurance and the food eaten at home are shared; clothes, hobbies, haircuts, phone contracts, your own car, gifts for your own family and lunches out are yours. This is what makes an uneven split tolerable for the higher earner, because it means paying more of the shared life rather than funding the other person's discretionary spending.

Proportional up to a ceiling

Apply income proportions, but cap anyone's contribution at, say, 45% of their own take-home pay. It does nothing in ordinary months and quietly protects the lower earner when the shared costs spike.

Equal split with a rebalancing transfer

Split every expense equally so the running record stays simple, then make a single monthly transfer from the higher earner to the lower one to land on whatever ratio you agreed. It is arithmetically identical to an uneven split and much easier to keep track of, and it makes the subsidy explicit — which some couples like and others dislike.

Whichever you choose, write down four things: the list of what counts as shared, the definition of income you are using, each person's resulting monthly figure, and the date you will look at it again. Monthly amounts, not percentages you re-derive from scratch each time.

Agree when you will change it

The thing that breaks an income-based split is not the maths. It is that incomes move and the split does not, and a year later somebody is paying a percentage that stopped being true last spring while resenting it in silence. Silence is the failure mode, so make revisiting the split a scheduled event rather than a confrontation somebody has to initiate.

Two mechanisms, and you want both:

• A cadence. Once a year is enough for most couples — put it next to the tenancy renewal or a January evening — and once every six months if either income is irregular. The point of a fixed date is that raising money is no longer a decision; it is just what happens in January.
• Triggers. Agree now that the split is recalculated whenever a named thing happens: either of you gets a rise or a cut, changes hours, loses a job, starts or ends parental leave, moves, or takes on a new recurring cost. A trigger converts an awkward announcement into a routine one, because you agreed in advance that this is what a pay rise means.

Two conventions that keep the review small. Use a threshold, so you do not redo the sums for a £40 change — recalculate only if someone's income has moved by more than, say, 5%. And keep the method stable even when the numbers change: revisiting the ratio is routine maintenance, whereas switching from proportional to equal leftover is a new agreement and deserves a proper conversation.

The contributions that are not money

Every honest article about this has to stop at the same wall. One of you does most of the cooking, the laundry, the admin, the calls to the energy supplier, the childcare pick-ups. One of you put £3,000 down as the deposit, or owns the car the household uses, or drove the move. None of that is in any of the formulas above, and no formula fixes it.

Resist the urge to price it. Putting an hourly rate on housework turns a relationship into a contract with a rate card, invites an argument about whose hour is worth more, and tends to end with the lower earner's time valued lower — which is the opposite of what the exercise was for. Time and money are not interchangeable in a way you can settle to two decimal places.

What does work is naming it explicitly, in the same conversation as the money, without converting it:

• Write down who does what alongside the financial split, so the unpaid work is visible in the agreement rather than invisible around it. Being counted is most of what people are asking for.
• Rebalance in kind first. If the effort is lopsided, move a task rather than a payment — swap the cooking or the admin. If you would rather buy the problem away and can afford it, pay for a cleaner from the joint pot and treat that as a shared cost.
• Treat a one-off capital contribution as a debt or a gift, and say which. A deposit is money held and usually returned, not a monthly expense, so it does not belong in the split. Either it is a loan to be repaid when the deposit comes back, or it is a gift. Both are fine; leaving it undefined is what turns into a bad conversation in two years. The same goes for one person buying the sofa or the washing machine.
• Do not offset money against effort by stealth. "I pay more, so I do less cleaning" may be a deal you both accept, but only if it was actually agreed rather than assumed.

And if the two of you have quite different views about how much a bigger income should buy in influence, that is a values conversation, not a maths one. Have it directly; the arithmetic will not settle it for you.

Somebody still has to keep the record

Here is the part that decides whether your uneven split actually happens. Once the ratio is not 50/50, nobody can do the sums in their head at the till. A 60/40 rule means every shared expense has two numbers, and the only way it survives is if somebody writes them down — a shared note, a spreadsheet, a joint account statement, or an app. Any of those beats memory, and memory is what most couples are quietly using.

The joint-account route sidesteps the record-keeping almost entirely, which is why it is worth considering even if you find it unromantic: if all shared costs leave one account funded by two uneven standing orders, the statement is the ledger. The case for a running record instead is that not everything can go through the joint account — someone pays for the food shop with their own card, someone books the boiler service — and those are exactly the expenses that get forgotten.

We make one of the tools for this, so read this paragraph accordingly. Splitright is a free app for iPhone, iPad and Android that keeps a running record of who paid for what and what that leaves owing. There is no account and no sign-up: one person creates a group, shares a six-character code, and the other opens the same group from their own phone. No adverts, no trackers. For this topic the relevant feature is that an expense can be split by weighted shares as well as equally or by exact amounts — so a 60/40 income split goes in as shares of 6 and 4 (or 3 and 2) on each shared expense, and a fixed rent goes in as exact amounts, which always add to the total. It records who owes whom; it does not move money, connect to a bank or settle anything for you, and it will not choose your ratio.

• Download for iPhone
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Related: splitting expenses without making anyone sign up, splitting rent unevenly and the bill split calculator.

Common questions

How should couples split bills when one earns more?

The usual answer is an income-proportional split: add both take-home incomes, work out each person's percentage of that total, and apply those percentages to the shared costs. Both then pay the same fraction of their own pay, so the burden is equal even though the amounts are not. It needs both incomes on the table, and it needs recalculating whenever one of them changes.

What is an equal leftover split?

It is a split chosen so that both people have the same amount of money left after the shared costs are paid. Add both incomes, subtract the shared costs, divide what remains by two, and each person pays their income minus that figure. At large income gaps it can ask the lower earner to pay nothing at all, or even to receive money, which is why some couples cap it.

Should you use gross or take-home pay to split costs?

Take-home pay, because that is the money that can actually pay a bill. Use the figure that lands in the account each month, averaged over a few months if it varies, and decide in advance how you treat bonuses, overtime, benefits and income from a second job. Write the chosen definition down, because the definition is what people argue about later, not the arithmetic.

How often should you revisit the split?

Once a year as a matter of routine, plus immediately whenever an agreed trigger happens: a pay rise or cut, a job loss, a change in hours, a move, or a new recurring cost. Naming the triggers in advance is what stops the split quietly going stale, because the usual failure is nobody raising it rather than anybody miscalculating.