How this calculator works
Everyone uses the kitchen, living room and hallway equally, but not everyone has the same bedroom. So part of the rent (the shared-space share) is split evenly, and the rest is split by each bedroom's square footage. A 50% shared share is a common middle ground; raise it if the bedrooms are small and the common areas large. Utilities are split equally on top.
- Shared part = rent × shared-space % ÷ number of bedrooms (paid equally).
- Room part = rent × (1 − shared-space %) × bedroom sq ft ÷ total bedroom sq ft.
- Each person pays shared part + room part + utilities ÷ number of people.
Worked example
With these inputs: total monthly rent $2,400; share of rent for shared space 50%; utilities and internet per month $150; bedroom 1 180; bedroom 2 140; bedroom 3 110.
The result is bedroom 1 (largest) pays each month $952.33, with bedroom 3 (smallest) pays $756.98 and an equal split would be $850.00. Adjust before you settle: a private bathroom, a balcony or a parking space is often worth an extra $50–$150 a month, taken off the others' shares equally.
Why split rent by room size
An equal split is simple, but the person in the 110 sq ft room is paying the same as the one in the 180 sq ft room. Splitting the whole rent by square footage goes too far the other way, because everyone uses the kitchen, living room and bathroom equally. Counting part of the rent as shared space and splitting only the rest by size is the middle ground most roommates accept.
In the example each person pays $400 for the shared space, and bedroom space costs $2.79 per square foot. An equal split would be $850 each with utilities, so the biggest room pays $102.33 more and the smallest $93.02 less.
Picking the shared-space percentage and other adjustments
50% works for most apartments. Raise it toward 60–70% when bedrooms are small and the living areas large, or lower it when one bedroom is much bigger than the rest. A private bathroom, balcony or parking space is usually priced as a flat extra, often $50–$150 a month, taken off the others equally.
Check that each share is affordable. HUD's long-standing rule of thumb is that housing costs above 30% of income are a burden, and the rent affordability calculator applies it. For bills split by income rather than room size, use the split bill calculator, and put your share in a bill tracker so rent day is never missed.
Sources
Frequently asked questions
How do you split rent fairly by room size?
Split part of the rent equally for the shared space (50% is common), then split the rest in proportion to each bedroom's square footage. $2,400 with rooms of 180, 140 and 110 sq ft gives $902.33, $790.70 and $706.98.
Should the person with the biggest room pay more rent?
Usually, yes. A larger bedroom is more private space, so most roommates pay more for it. Splitting only the bedroom share by size keeps the difference reasonable.
How do you split rent with a private bathroom?
Calculate the room-size split first, then add a flat monthly amount for the private bathroom to that room and take the same amount off the other rooms equally.
Should couples sharing a room pay more?
Often the couple pays for one bedroom but two shares of the utilities and a larger share of the shared space, since two people use it. Agree on it before signing the lease.
How should roommates split utilities?
Equally per person is the norm, because everyone uses the shared spaces and appliances. In the example, $150 of utilities is $50 each.