Rent split by room size calculator

The rent is first divided into two pots, in proportion to floor area: one for the bedrooms, one for the shared space you entered. The bedroom pot is then split in proportion to each room's size, while the shared pot is divided strictly equally, because the living room, kitchen and bathroom serve everyone the same way.

If you leave the shared area blank, the whole rent follows bedroom size alone. That is the simplest rule, but it makes the largest bedroom pay proportionally more for spaces everybody uses equally.

Use the private floor area written on the tenancy agreement, or measure it yourself: length × width, rounded to the nearest square metre. For the shared area, add up the living room, kitchen, bathroom, toilet and hallway. Being one or two square metres off barely moves the result.

Do not count space only one person can use, such as a balcony reached through a single bedroom. Add it to that bedroom's private area instead.

A dark ground-floor room and a bright room with a balcony are not worth the same, even at identical size. Nothing stops you from entering an adjusted area — 90% or 110% of the real square metres — as long as the rule is agreed together and written down somewhere everyone can find it.

Rent is only part of a shared household's budget. Groceries, variable bills and the money people front for each other are far easier to follow in a shared expense group than in a spreadsheet.