Fifty-fifty feels like the neutral option. Nobody has to disclose anything and the maths takes two seconds. It also quietly hands the higher earner a much easier life, because an equal share of a $2,000 rent is a rounding error on one salary and most of a month on another. That gap is why so many people start looking up how to split bills fairly by income somewhere around month four of living together.
The fix is not complicated. It's one percentage, worked out once, and then a decision about which costs it applies to. The awkward part is the conversation, and that's the part worth getting right first.
Why an equal split stops feeling equal
Say one of you takes home $3,200 a month and the other takes home $4,800. Shared costs come to $2,400. Split down the middle, that's $1,200 each. The first person has $2,000 left, the second has $3,600. One of them can absorb a dental bill without thinking about it. The other is deciding between a train ticket home and a new pair of boots.
Same number, very different month. The lower earner starts declining dinners out and feeling like the boring one. The higher earner starts paying for things informally to smooth it over, which creates a different sort of imbalance, the kind nobody writes down and everybody remembers.
Nobody resents the number on the bill. They resent what's left in the account at the end of the month, and an equal split is very good at hiding that difference.
How to split bills fairly by income, with the actual maths
The standard approach is proportional. You each pay the share of the shared costs that matches your share of the combined income. Four steps, fifteen minutes, once.
- Use take-home pay, not salary. What actually lands in the account after tax, pension and student loan. Gross figures flatter whoever has the bigger deductions and make the split wrong from the start.
- Add both numbers together. In the example above, $3,200 plus $4,800 is $8,000 a month between you.
- Work out each person's percentage. $3,200 of $8,000 is 40 percent. $4,800 is 60 percent. Round to whole numbers, nobody needs decimal places here.
- Apply those percentages to the shared pot. On $2,400 of shared costs, that's $960 and $1,440. Now the lower earner keeps $2,240 and the higher earner keeps $3,360, which is still a real difference, just not a punishing one.
Then set up a standing transfer rather than settling up from memory each month. One joint account, or one person pays the bills and the other sends their share on payday. Anything that relies on somebody remembering to ask for money decays inside two months.
Which costs should be proportional and which should be equal
Here's where I'd push back on the pure percentage method. Applying one ratio to literally everything turns every coffee into an accounting exercise, and it also quietly says the lower earner gets a cheaper version of every shared decision.
The split most people land on treats two kinds of spending differently. Fixed costs that you can't opt out of go proportional: rent, utilities, internet, council tax or property tax, insurance, the weekly food shop. Optional shared spending goes equal: the restaurant you both chose, the concert tickets, the weekend away. The logic is that you can't decline your share of the heating, but you can decline a $90 dinner, and if you're both saying yes to it you're both saying yes to the price.
There's a third method worth knowing about, where you each contribute whatever leaves you with the same amount of disposable income. It is arguably the fairest version and I'd still usually skip it. It needs total transparency about every number either of you has, and it has to be redone whenever anything changes. Fair on paper, brittle in practice.
How to have the conversation without it turning into a negotiation
The reason this gets left so long is that asking someone what they earn feels like an accusation. It helps to put the proposal first and the numbers second, so the ask is about a method rather than a judgement.
Something like: “I think we should pay the fixed stuff in proportion to what we each take home, and split the fun stuff evenly. Want to work out the percentages?” That frames it as a shared system rather than one person asking the other for a discount. A few things worth agreeing in the same sitting:
- What counts as shared. Groceries almost always. Streaming subscriptions, cleaning products and the shared car are the ones that cause arguments later, so name them now.
- When you'll revisit it. A pay rise, a job loss or a move changes the ratio. Agreeing to recheck every six months stops it being a loaded conversation when it happens.
- What happens with debt. Someone paying down a large loan has less real disposable income than their payslip suggests. You can either ignore that or build it in, but decide out loud.
- Who pays what, mechanically. Name the account and the day. Vague arrangements are how people end up owing each other four months of internet.
If you're housemates rather than partners, the rules of thumb are similar but the rooms complicate it, and that's covered properly in the post on splitting rent with roommates.
Keeping track once you've agreed the split
An agreed percentage still falls apart if nobody logs the shared spending. The rent and the utilities take care of themselves because they're standing orders. It's the groceries, the taxi, the vet, the thing one of you covered because the other's card was upstairs. Those are small, constant, and they're where the quiet scorekeeping starts.
Bud handles this side of it. Logging a shared expense takes about seven seconds, you can split it there and then rather than in a separate app, and on an iPhone the Action Button will open a new expense before you've put your card away. There are no bank logins involved at any point. It's free to download, and Bud Plus is $1.99 a month or $15.99 a year. If your household already has a pile of history in Splitwise, you can import it instead of starting from zero.
Whatever you use, the habit matters more than the tool. Log it when it happens, because reconstructing a month of shared spending from bank statements is miserable and nobody does it twice. A short weekly money check-in is usually enough to catch a drifting split while it's still a five minute fix. One-off group spending is its own small nightmare, covered in splitting bills with friends.
When fifty-fifty is still the right answer
Proportional isn't automatically better. If your incomes are within about ten percent of each other, the difference is small enough that the admin costs more than the fairness gains. If one of you strongly prefers the simplicity and genuinely isn't bothered by the gap, that preference counts. And if you're sharing with people you don't know well, an even split keeps everyone's finances private, which is worth something.
The failure mode to watch for is agreeing to fifty-fifty because bringing it up felt rude, then spending a year feeling squeezed about it. That's the version that ends badly. Pick a method on purpose, write it down somewhere you'll both find it, and look at it again when something changes.
Track your money in seconds, not spreadsheets.
Bud is free to download, built for iPhone, and never asks for a bank login.
