Split rent by room size
For agreeing the rent before anyone moves in. For the bills and the shared shop afterwards, who owes whom sorts out who paid what.
When one bedroom is twice the size of another, halving the rent isn't fair and everyone knows it. This works out what each room should actually cost.
The kitchen, the living room and the hallway belong to everyone, so that slice is divided equally. The rest follows the bedrooms.
To the penny, every time. If it doesn't divide evenly, the leftover goes to the largest room.
Why you can't just divide by square footage
The obvious method — add up everyone's bedroom area and split the rent in proportion — overcharges whoever has the big room and undercharges the small one. It assumes you're only paying for the room you sleep in.
But you're not. The kitchen, the living room, the hallway and the shared bathroom are used identically by everybody, and in most flats they're a third to a half of the floor area. Nobody should pay more for a sofa because their bedroom is bigger.
So the rent splits in two. The shared slice is divided equally, head by head. The remainder follows the bedrooms in proportion to their size. That's the method this calculator uses, and it's the one that survives a conversation at the kitchen table.
What else is worth charging for
Square footage isn't the only difference between rooms. An ensuite is worth paying for, and this adds roughly 15% to a room's weight when you tick it.
Other things people reasonably argue about: a balcony, a built-in wardrobe, which room gets the morning light, which one faces the main road, and who has to walk through the living room to reach the bathroom. There's no formula for those. Agree a flat adjustment and write it down.
What matters most is that the method is explicit before anyone moves in — not renegotiated in month four.
Rent is the easy month. It's everything else.
Electricity, internet, the shared shop, the thing someone bought for the kitchen. Stub keeps the running total for the four of you — photograph the bill and it works out who owes what. Free, with no daily limit.
Nothing you type here is sent anywhere or stored. Stub records what people owe each other; it never holds or moves money.