How to split rent when you earn different amounts

Two people who earn very different amounts and share one address eventually hit the same question, usually somewhere between the third and the fourth month: is half each actually fair? It is a genuinely hard question, and it is made harder by the fact that most people try to answer it without ever writing down the numbers it depends on.

Half each is fair in dollars and not in effort

An even split means the same amount leaves both accounts. That is where the fairness ends. If rent is $2,400 and one person takes home $4,200 while the other takes home $3,100, an even split is 29% of one salary and 39% of the other. Same apartment, same bedroom, ten points of difference in what it costs them.

Nobody feels a percentage, though. What they feel is the last week of the month, and the person paying 39% hits it noticeably earlier. That mismatch is why this argument tends to arrive as irritation about something else entirely.

The proportional split, and what it actually does

The alternative is to split by income: add both take-home figures, work out each person's share of the total, and apply that share to the rent. In the example above that is roughly $1,380 and $1,020, and both people are handing over about 33% of what they earn.

This is not more generous, it is differently distributed. The higher earner pays more dollars; both people give up the same slice of their month. Which of those two things you think fairness means is the actual disagreement, and it is worth having out loud rather than through the rent.

Room size, for housemates

Where the people sharing are not a couple, income tends to feel like the wrong basis: your salary is your business and it has nothing to do with the apartment. Square footage is the usual answer instead. Add up the rooms, take each person's share, apply it to the rent, then adjust by hand for the ensuite or the room facing the street.

Nobody should pretend that produces a precise answer. It produces a defensible starting point, which is all a house needs.

Three things worth agreeing at the same time

• What happens when somebody's income changes. A raise, a redundancy, a switch to freelance. If the split is proportional, decide now whether it moves automatically or gets renegotiated, because doing it in the moment is much harder.
• Whether the split applies to everything or just rent. Most households pick a rule for rent and then never apply it to the power bill, and the power bill is where the drift happens.
• What is shared and what is not. Groceries usually are. A gym membership usually is not. Saying so early is much easier than saying so after six months of resentment.

The part that breaks, every time

Almost nobody gets the rent wrong. It is one number, it is the same every month, and both people know it. What breaks is everything else: the utility bill that moved, the internet that is on one person's card, the four subscriptions nobody has counted, the groceries that were meant to alternate.

Those are small individually and large together, and they are the ones that quietly stop being split at all. Six months later one person has covered a few hundred dollars more than they meant to, neither of them decided that, and neither of them can prove it.

💡If you take one thing from this: agree the rule once, then apply it to the whole month rather than to the biggest line in it. The rule is easy. The applying is the bit that needs help.