Rent split calculator: divide the rent by room size
Three roommates, one $2,400 apartment, and one bedroom that is clearly bigger than the other two. Splitting the rent three ways is quick. Whether it is fair depends on the floor plan.
5 min read
Rent split calculator: each share by room size
Enter the rent, the apartment's total area and each bedroom's area: shared space is split equally per person, each bedroom by its size, and the shares add up to the rent to the cent. No account, no email, and nothing is stored.
The form is filled in with this article's example. Replace the names and the figures, or clear everything to start from scratch.
The example's result
| Person | Bedroom | Shared space | Pays | vs equal split |
|---|---|---|---|---|
| Jordan | $480.00 | $417.78 | $897.78 | +$97.78 |
| Casey | $373.33 | $417.78 | $791.11 | −$8.89 |
| Riley | $293.33 | $417.78 | $711.11 | −$88.89 |
| Total | $2,400.00 |
Sum of the shares: $2,400.00, exactly the rent.
Split equally, each of the 3 would pay $800.00. The last column shows the difference.
How it was calculated
- Shared space: 900 minus 430 of bedrooms leaves 470, which costs $1,253.33 of the rent; divided by 3 people, $417.78 each.
- Bedroom 1 (Jordan): 180 out of 900, $480.00.
- Bedroom 2 (Casey): 140 out of 900, $373.33.
- Bedroom 3 (Riley): 110 out of 900, $293.33.
- Each person pays their bedroom plus their part of the shared space.
Here, at least one share fell between two cents. The rounding rule: each share is first rounded down to the cent, then the missing cents go one by one to the shares that lost the most; on a tie, to the larger share, then to the first in the list. The bedroom and shared-space amounts above are rounded on their own, to explain the calculation; the shares are what adds up to the rent.
Paying back the rent
Jordan pays the landlord $2,400.00. Each month:
- Casey pays Jordan $791.11
- Riley pays Jordan $711.11
This calculator applies one way of splitting rent, to agree on between you. It does not cover utilities, deposits or any lease or legal rule.
To split rent by room size, pay the shared space (living room, kitchen, hallway, a bathroom everyone uses) in equal shares per person, and pay each bedroom in proportion to its area. Enter the rent, the apartment's total area and each bedroom's area in the calculator above: it gives each roommate's share to the cent, and the shares always add up to the rent.
The calculator works in square feet or square meters, as long as every measurement uses the same unit. It does not need an account, and a calculation stores nothing.
Why not split it equally?
An equal split is fine when the bedrooms are close in size. When one is half as big again as another, the person in the small room pays for space they never use, and that tends to come up again every month.
Splitting by bedroom size alone goes too far the other way: it treats the kitchen and living room as if they belonged to whoever has the biggest bedroom. The method used here sits between the two. Everyone has the same access to the shared space, so everyone pays the same for it; the bedrooms are private, so each one is paid by its size.
How the calculation works
- Divide the rent by the apartment's total area: that is the rent per square foot.
- Multiply each bedroom's area by that figure: that is the cost of each bedroom.
- Subtract the bedrooms from the total area: what is left is shared space. Multiply it by the rent per square foot and divide the result by the number of people living there.
- Each person pays their bedroom plus their share of the shared space.
Count an en-suite bathroom, a private balcony or a walk-in closet as part of the bedroom it belongs to: it is private space, so it is paid like the bedroom.
When a share does not come out in whole cents, the calculator rounds each share to the cent and gives the leftover cents to the largest remainders, so the total is always the rent.
A couple in one bedroom
A couple sharing a bedroom pays for one bedroom but uses the shared space as two people. In the calculator, enter two people in that room. In the example above, if Jordan's partner Sam moves in with them, the shared space is divided by four instead of three: $313.33 per person. Jordan and Sam pay $553.33 each, $1,106.67 for the two of them, Casey pays $686.67 and Riley $606.67. The total is still $2,400.00.
When you don't know the total area
Leases and listings do not always give the apartment's size. Measuring the bedrooms takes five minutes with a tape measure; the shared space is harder. If you cannot measure it, agree on the share of the rent that pays for shared space, for example half: the calculator divides that part per person and the rest by bedroom size. In the example, half the rent as shared space gives $400 per person, plus $1,200 split between the bedrooms by size, so Jordan pays $902.32, Casey $790.70 and Riley $706.98.
What size does not capture
A bedroom with the only window onto the street, a room next to the front door, or the one with the big closet: size is a starting point, not the whole story. The simplest way to account for it is to add a few square feet to the better room, or take a few off the worse one, before running the calculation. Agree on it once, when everyone moves in, and write it down.
Rent is only one of the bills. Utilities, internet and groceries are usually split differently, in equal shares or by use: how to split bills with roommates covers those. If incomes are very different and you would rather split by income, see how to split expenses by income.
The security deposit and moving out
The security deposit is usually split in the same shares as the rent, and returned in the same shares. When one roommate moves out and someone else takes the room, the newcomer often pays the leaver their share of the deposit directly, so the landlord does not have to refund and collect it again. Write down who paid what part of the deposit on the day you move in: it is the number everyone has forgotten when the lease ends.
When one person pays the landlord for everyone, the others pay them back their share each month. If the same roommates also share other bills, it is simpler to track everything in one tally and settle the balance once a month: who owes who explains how that balance is worked out.
Keeping the split in Kotisso
Kotisso is a free app for sharing expenses with the same people over time: the rent goes in once as a monthly expense with each roommate's amount, next to the utilities and groceries. It shows each person's balance to the cent and who pays back whom; the transfers themselves happen outside the app. The button under the calculator creates your group with these shares when you sign up.
Frequently asked questions
Should the person with the biggest room pay more rent? Usually yes, for the bedroom part only. Shared space is used equally, so it is paid equally; the larger bedroom costs more in proportion to its extra area.
How do you split rent with a couple in one room? Count the couple as two people for the shared space and as one bedroom for the private space. In the example, that brings the couple to $1,106.67 for the two of them instead of $897.78 for one person.
What about a bedroom with a private bathroom? Add the bathroom's area to that bedroom. It is private space, paid at the same rate per square foot as the bedroom.
Does the calculator save my data? No. A calculation stores nothing and needs no account. If you want to keep the split, the button under the results creates a Kotisso group with the same shares after you sign up.
