How the rent split calculator works
Splitting rent evenly is simple, but it ignores that bedrooms differ in size. This calculator splits rent between roommates in two parts. One part pays for the space you all share, like the kitchen, the living room and the hallway, and everyone pays the same amount for it. The other part pays for the bedrooms and is split by their size in square feet or square meters, so a bigger room pays more. What counts as fair is up to you and your roommates. The calculator only does the math for the rule you choose.
An example with three bedrooms
Alex, Sam and Jo rent a flat for $2,400 a month. Their bedrooms have 150, 120, 100 square feet, 370 in total, and they set the shared space share to 50%.
- Shared space: 50% of $2,400 is $1,200, so each of the three pays $400.
- Bedrooms: the other $1,200 is split by size. Alex pays 150 ÷ 370 of it, Sam 120 ÷ 370 and Jo 100 ÷ 370.
| Roommate | Bedroom | Shared part | Bedroom part | Pays |
|---|---|---|---|---|
| Alex | 150 sq ft | $400.00 | $486.49 | $886.49 |
| Sam | 120 sq ft | $400.00 | $389.19 | $789.19 |
| Jo | 100 sq ft | $400.00 | $324.32 | $724.32 |
The three shares add up to exactly $2,400.00.
Extras: private bathroom, balcony or a smaller window
Some rooms have something the others do not. You can add an extra to any room in two ways:
- As a percentage: the room counts that much larger in the bedroom split. +10% on a 120 square feet room makes it count as 132. In an equal split, it raises that person's share of the rent by the same ratio against the others.
- As a fixed amount: that room pays the amount on top, and the rest of the rent is split as before. If Jo's room above has a private bathroom and the group agrees it is worth $100 a month, Jo pays $794.14, Alex $849.55 and Sam $756.31.
A negative extra lowers a room's share, for example for a room without a closet. The total always stays the rent.
Why the shares add up to the cent
Rent rarely divides into whole cents. If every share is simply rounded, the total can be a cent or two off. This calculator uses the largest remainder method: every share is first rounded down to the cent, then the leftover cents go one at a time to the people whose exact share was closest to the next cent. The shares then add up to the rent exactly. For currencies without cents, like the yen, it works the same way with whole units.
How to use the rent split calculator
- 1Enter the total rent per month and choose by room size or an equal split.
- 2For a split by size, set the shared space share and enter each bedroom's size and how many people live in it.
- 3Add extras for a private bathroom or a balcony if you agreed on them, then copy the result or a link to share with your roommates.
To split a restaurant bill instead, use the tip and split calculator. To measure a room, the square footage calculator works out the area from its length and width.
Frequently asked questions
How do you split rent by room size?
Decide which part of the rent pays for shared space like the kitchen and living room, and split that part equally. Split the rest by bedroom size: each room pays its square feet divided by the total square feet of all bedrooms. With $2,400 rent, 50% for shared space and bedrooms of 150, 120 and 100 square feet, the shares are $886.49, $789.19, $724.32.
What percentage should go to shared space?
There is no fixed rule. At 0% the whole rent is split by bedroom size, at 100% everyone pays the same, and values in between mix the two. Try a few values with your roommates and agree on one together. The calculator shows every share right away.
How do I account for a private bathroom or a balcony?
Add an extra to that room, either as a percentage or as a fixed amount. A percentage makes the room count that much larger in the size split. A fixed amount is paid on top by that room, and the rest of the rent is split between everyone as before, so the total stays the same.
What if a couple shares one room?
Set that room to 2 people. The shared space part is split per person, so the couple pays two shares of it, and the bedroom part of their room is split between the two of them.
Why does one person pay a cent more?
Rent rarely divides into whole cents. The calculator rounds every share down to the cent, then gives the leftover cents one by one to the people whose exact share was closest to the next cent. That way the shares add up to the rent exactly, never a cent more or less.