How to split shared household expenses when you earn different amounts
Fifty-fifty, proportional to income, or one pot: each rule is fair by a different definition and each breaks somewhere. How the three compare, and what to do about unpaid work, debt and savings.
Two people live together. One earns considerably more than the other. Rent, energy, food and everything else has to be paid. There is no arithmetic that resolves this, because the disagreement is not arithmetic — it is about what fairness means, and there are at least three defensible answers.
What follows is a comparison of the three, with the failure mode of each stated plainly. The aim is not to tell you which to pick. It is to make sure that whichever you pick, you picked it rather than drifting into it, and that you know in advance where it will hurt.
Option one: split everything evenly
Each person pays half of every shared cost. It is simple, requires no disclosure of income, and preserves a clean sense of independence. For housemates and for couples with similar incomes it is usually right, and its simplicity is a genuine virtue — arrangements that need a spreadsheet tend to be abandoned.
The problem appears as soon as incomes diverge. Consider a household where one person earns twice what the other does and shared costs come to half the smaller income. After paying their half, the lower earner has very little discretionary money left; the higher earner has a great deal. Both paid "the same". They are not living in the same household.
In practice this usually resolves in one of two unpleasant ways: the lower earner quietly goes into debt or stops participating in anything optional, or the household downgrades its housing and food to what the lower earner can manage evenly, which the higher earner comes to resent. Neither is a stable arrangement, and both are usually discovered late.
Option two: split in proportion to income
Add both incomes, work out each person’s share of the total, and each pays that share of the shared costs. If one earns sixty thousand and the other forty, the split is sixty-forty on every joint bill. The result is that both people are left with a similar proportion of their income for themselves, which is a reasonable definition of equal burden.
This is the arrangement most likely to be described as fair by people who have thought about it, and it has real problems.
- It requires disclosing income, and it requires updating whenever income changes, which people forget to do for a year at a time.
- "Income" is ambiguous for anyone self-employed, on variable hours, on commission, or holding assets. Two people can be honest and still disagree about the number.
- It can turn into a purchasing-power argument: the higher earner is paying more, and may feel entitled to more say over what the household buys. That is a real and corrosive dynamic, and it should be named explicitly at the start — the higher share buys an equal household, not a larger vote.
- It says nothing about savings. Proportional on costs plus each person saving whatever is left means the higher earner accumulates wealth much faster, which matters enormously if the relationship ends or if one person left the workforce for the household.
The last point deserves emphasis because it is where proportional splits most often turn out to have been unfair in retrospect. If one person reduced their earnings to look after children or to support the other’s career, an arrangement that is fair on monthly cash flow can still produce a very unequal position after ten years.
Option three: one pot
All income goes into a joint account. All spending comes out of it. There is no split because there is nothing to split; there is a household with an income and expenses.
This is the simplest arrangement to run and the one that handles unpaid work, career sacrifice and unequal earning naturally, because it never distinguishes whose money it is. Many long-established couples end up here.
What it requires is a high level of trust and, in practice, a personal allowance each — an amount that does not need to be discussed or justified. Households that pool everything without any private money tend to produce either a permission dynamic, where one person feels they must ask, or hidden spending, which is corrosive in a different way. The allowance is not a concession to selfishness; it is what makes full pooling survivable.
It is also worth being clear-eyed: full pooling assumes the relationship continues. Untangling a pooled household is significantly harder than untangling a split one, and that is a cost, not a reason against, but it should be a known cost.
The things every arrangement forgets
Unpaid work is work
Cooking, cleaning, childcare, appointments, admin, remembering that the insurance renews. In most households this is unequally distributed and it is invisible to every split rule above, all of which look only at money. A split that is exactly proportional on income and wildly disproportionate on hours is not obviously fair.
There is a well-known strand of economic research questioning whether households behave as a single decision-making unit at all. A frequently cited example is the analysis by Lundberg, Pollak and Wales of a UK policy change in the late 1970s that shifted child benefit payments from fathers to mothers; spending patterns appeared to shift with it, which is hard to reconcile with the idea that it does not matter who receives the money. The finding is contested and has been re-analysed several times, and one policy change in one country is a narrow base. But it is a reasonable prompt for a household question: does it matter here who earns it and who receives it? If the honest answer is yes, no split rule will fix that on its own.
Debt brought into the household
Student loans, a car loan, a credit card from before you met. The common position is that pre-existing debt stays personal, which is defensible, but it interacts badly with proportional splitting: the person with the debt has less usable income than their gross figure suggests. Some households split proportionally on income after debt service for exactly this reason. Whichever you choose, decide it explicitly rather than letting it be a source of quiet resentment.
Savings and pensions
If you split costs but save separately, you are running two financial futures in one household. That may be exactly what you want. It should be a decision, not an oversight, and it is worth revisiting whenever earnings change substantially.
Making any of them work in practice
Whichever rule you pick, three things determine whether it survives.
- Write down what counts as a shared cost. The rule is easy; the boundary is where the arguments are. Is a car a shared cost when one person drives it to work? Is a takeaway on a night when only one of you eats it? Decide the awkward cases while nobody is annoyed.
- Keep one record that both people can see. Splitting arrangements collapse when the two people have different beliefs about what was spent. A shared ledger where each entry says who paid removes the reconstruction argument entirely, which is most of the argument.
- Review it on a schedule, not when someone is upset. Twice a year, or whenever income changes. Arrangements that were fair three years ago are frequently not fair now, and the person disadvantaged by the drift is usually the one least comfortable raising it.
If you are settling up between separate accounts, the mechanics matter less than the record. Fambook is a shared ledger rather than a settle-up app — it will not compute who owes whom — but each entry carries who spent it and the statistics screen breaks a period down by member, which gives you the numbers the arithmetic needs. Doing the division yourself once a month is not the hard part; agreeing what the numbers are is.
Frequently asked questions
Is splitting bills 50/50 unfair if we earn different amounts?
It is fair by one definition — equal contribution — and unfair by another — equal burden. On significantly unequal incomes, an even split leaves the lower earner with much less discretionary money, which usually surfaces as debt or as withdrawal from anything optional. Neither is a good outcome, so it is worth choosing deliberately rather than by default.
How do I calculate a proportional split?
Add both incomes to get the household total, divide each person’s income by that total for their share, and apply that share to each joint bill. Sixty and forty thousand gives a sixty-forty split. Agree in advance whether "income" means gross, net, or net after servicing pre-existing debt — that choice can move the split by several points.
Should we combine finances completely?
It is the simplest arrangement to run and the one that handles unpaid work and career sacrifice most naturally, and it needs high trust plus an unquestioned personal allowance each. Without the allowance, pooling tends to produce either a permission dynamic or hidden spending.
What if one of us does most of the housework?
No money-based split accounts for it, because all of them look only at money. Some households adjust the split, others rebalance the work, and others simply name it and accept it. The failure mode is not choosing — the imbalance persists and becomes a grievance rather than a decision.
How often should we revisit the arrangement?
Twice a year, and whenever either income changes substantially. Put it in a calendar. Arrangements drift out of fairness slowly, and the person disadvantaged by the drift is usually the one who finds it hardest to raise.
Do we need a joint account to do this?
No. Plenty of households keep separate accounts and settle up monthly. What you do need is one record both people can see, because the argument is almost never about the division — it is about what was actually spent.
Try it for one month
Fambook gives a household one shared ledger: anyone can add an entry in seconds, every entry says who spent it, and the month adds up in one place instead of two. Records with no signal and syncs afterwards. Recording, categories, budgets, statistics, CSV import and export, sync and sharing for two people are free — the subscription only buys you less typing.