How to split rent fairly when the rooms aren't the same size

Three people move into a flat. One bedroom is big and bright, one is fine, and one fits a bed and not much else. Splitting the rent three ways feels easy on day one and unfair by month three, usually to whoever got the small room.

There’s no single right answer, but there are a few methods that people agree on quickly. Here they are, with numbers.

Four ways to split the rent

Equally. Everyone pays the same. It works when the rooms are close in size, or when the person with the smaller room is happy with the deal, for example because they also got the quieter street side. It’s the easiest to manage and the hardest to keep fair if the rooms really differ.

By bedroom size. Measure each bedroom and split the rent in proportion. It’s objective, but it treats the shared kitchen and living room as if they didn’t exist, so the big room ends up paying for a lot of space everyone uses.

Half equal, half by size. Split half the rent equally, for the shared space, and the other half by bedroom size. This is the one most groups settle on, because it accounts for both the rooms and the space everyone shares, and anyone can check the maths.

By features. Start from an equal split and adjust: a bit more for the room with its own bathroom or balcony, a bit less for the one next to the noisy stairwell. It’s flexible, but every adjustment is a small negotiation, so agree on all of them at once and write them down.

A worked example

Ana, Ben and Caro rent a flat for 1,800.00 a month. Their bedrooms are 16, 12 and 9 square metres. They go with half equal, half by size.

The equal half is 900.00, so each of them pays 300.00 for the shared space.

The other 900.00 is split by bedroom size. Together the bedrooms are 37 square metres:

• Ana: 16 / 37 of 900.00 = 389.19
• Ben: 12 / 37 of 900.00 = 291.89
• Caro: 9 / 37 of 900.00 = 218.92

Add the two parts together:

• Ana pays 689.19
• Ben pays 591.89
• Caro pays 518.92

That adds up to exactly 1,800.00. Compared with an equal split of 600.00 each, Ana pays 89.19 more for the biggest room and Caro pays 81.08 less for the smallest. Both differences are easy to explain to a flatmate.

If you’d rather work in percentages, that’s 38.29%, 32.88% and 28.83%.

Bills and groceries are a different question

Rent is about space. Bills are about use, and in most flats the use is close enough to equal that splitting them evenly saves a lot of arguing.

• Energy, internet and water: equal, unless someone works from home all day and offers to pay more.
• Shared groceries: cleaning things, oil, coffee, toilet paper. Equal, and only for the things everyone uses.
• Personal food: keep it off the shared tab. A flat where everyone buys their own food and splits only the basics has far fewer disagreements than one with a single grocery pot.

Whatever you choose, decide it when you move in. Changing the rules later always feels personal, even when it isn’t.

Keeping track month to month

Most of the trouble in a shared flat comes from small costs piling up. Ben pays the internet, Caro buys the vacuum bags, and Ana pays the landlord and waits to be paid back.

In split-cash, make one group for the flat and add costs as they happen:

1. Rent: add it as one expense paid by whoever pays the landlord. Choose “Amounts” and enter 689.19, 591.89 and 518.92, or “Percent” with the three percentages. split-cash checks that the parts add up to 1,800.00 before it saves.
2. Bills: add each bill when it’s paid, split equally.
3. Shared groceries: add them as they’re bought, split equally.

Everyone sees the same balance at any time. Once a month, or whenever the balances drift too far, open Balances: split-cash shows the fewest transfers that bring everyone back to zero. Make them, mark each one as paid, and start the next month clean.

split-cash doesn’t repeat the rent automatically yet, so it’s one expense to add each month. With the amounts already worked out, that takes a few seconds.

Questions people ask

What is the fairest way to split rent with unequal rooms? A common approach is to split half the rent equally, for the kitchen, bathroom and living room everyone uses, and the other half by bedroom size. It’s simple to explain and everyone can check the maths.

Should bills be split the same way as rent? Usually not. Most flats split energy, internet and water equally, because everyone uses them about the same, and keep the room-size split for rent only.

How do I record a rent split in split-cash? Add the rent as one expense paid by whoever pays the landlord, choose “Amounts” or “Percent”, and enter each person’s part. split-cash checks that the parts add up to the total before you save.

Can split-cash repeat the rent every month? Not yet. For now you add the rent once a month, which takes a few seconds once you know the amounts.

If you’re moving in with someone soon, make a group for the flat before the first rent is due. It’s free, and your flatmates join with a link.