There are two common ways to split rent in a shared house: everyone pays an equal share, or the total is weighted by room size. Which one feels fairer comes down to how different the rooms actually are. What matters more than the method, though, is getting it in writing before anyone moves in, because on a joint tenancy the landlord has no interest in how you carved up the total between yourselves.
Why this is a legal question, not just a fairness one
Until I looked it up, I hadn’t realised quite how different a joint tenancy is from splitting a bill between friends. Citizens Advice is blunt about it: if you have a joint tenancy, you are liable for the rent both jointly and individually, meaning that one or all of you can be held responsible for the whole rent. There’s a second type of arrangement too, where each person signs their own agreement for their own room: if you have your own individual tenancy agreement then you are liable to pay the rent, meaning only your own share of it. Most shared houses between friends run on the first kind, one joint tenancy with every name on it, and that’s the version where this distinction actually bites.
If someone doesn’t pay, who’s actually on the hook
Shelter’s guidance sets out what joint liability actually means day to day. On a joint tenancy, everyone on the tenancy agreement is responsible for the whole rent. If one housemate’s share doesn’t turn up, your landlord can ask the other joint tenants to pay the missing rent instead of chasing only the person who skipped it. Leave that unresolved for long enough and your landlord could try to evict all of you for any unpaid rent, the people who paid their share on time included.
What looks like an argument about fairness is really a question about who ends up covering someone else’s missing rent if it comes to that. An agreed figure per person, written down somewhere, settles afterwards who owes what. It gives the group something to point to if someone falls behind, rather than everyone’s half memory of a group chat from eight months back.
The two common ways to split it
Equal split. Total rent divided by the number of people. This works well, and is arguably the right call, when the rooms are close to the same size: similar floor area, similar light, nobody stuck with the box room or handed the en-suite. I wouldn’t argue against it in that case. It’s also the simplest to agree, and the easiest to explain to a new housemate who moves in halfway through a tenancy to replace someone.
Room-size split. Each room’s share of the rent comes from that room’s floor area as a proportion of the total floor area of all the bedrooms added together. Shared spaces, the kitchen, living room, bathroom, hallway, aren’t divided up this way, because everyone has equal access to them whatever size their bedroom is. Only the bedrooms themselves go into the sum. None of this is an official rule set by any government body or housing charity; there’s no formal UK guidance mandating a particular method, only, as covered above, guidance on what happens if the agreed amount doesn’t show up. It’s the method most people reach for once the rooms are noticeably different sizes, because it ties the figure to something measurable instead of an argument about who got the better view.
Neither method is more “correct” in a legal sense. The tenancy agreement and the law only require that the full rent arrives. How four housemates worked out their individual contributions to that total is nobody else’s business. The split is an agreement among the people living there; it isn’t a term the landlord has any say over. Agreeing a clear figure beats relying on an assumption everyone happens to share, right up until the day they don’t.
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Splitting by room size, in practice
Start by measuring each bedroom’s floor area in square metres, the same tape-measure job as checking whether furniture will fit somewhere else in a small flat. Add the areas together to get the total. Each room’s rent share is then its own area divided by that total, multiplied by the full rent: a 12m² room and an 18m² room in a flat with 30m² of total bedroom space split a £1,200 rent as £480 and £720, not £600 each.
The same logic holds with three or more rooms; it just means more arithmetic to check by hand. Three bedrooms of 10m², 12m² and 14m², 36m² of bedroom space altogether, splitting a £1,500 rent, come out to £417, £500 and £583: a different split from £500 each, even though the smallest and largest rooms here differ by less than half the gap in the two-room example above. Where one room has a genuine extra feature, an en-suite, private access, noticeably less noise from the street, it’s reasonable to agree a flat premium on top of the size-based figure rather than trying to measure the feature itself, as long as everyone agrees that premium before moving in, not after.
Working it out for an actual house
Doing this by hand for more than two or three rooms gets fiddly fast, which is why the housemate rent splitter exists: enter the total rent and each room’s size, and it works out each person’s share using either method above, equal or room-size, so the number everyone agrees on comes from a calculation rather than somebody’s best guess at what feels fair.
Writing it down before moving in, not after
Once a number exists for each person, it should live somewhere everyone can find it again later, not only in the head of whoever did the maths. A dated note of who agreed to pay what, kept alongside the tenancy agreement itself, fits into the same tenancy folder as everything else worth keeping. None of this changes the joint liability that Citizens Advice and Shelter both describe above. Instead, it turns “we never actually agreed that” into a question with a dated answer, which is the difference between a disagreement and an argument once someone’s share is late. The fixed costs of a first flat, beyond the rent itself, are covered in running a home on a first-job salary.
