Split rent by square footage: enter the total rent and each roommate’s room size, plus any shared area, to get each person’s monthly share.
Rent Split by Square Footage Formula
Splitting rent by room size charges each roommate in proportion to the private space they get. When the shared area is divided evenly, each person’s share is:
Share = Rent * (Private + Common / n) / (Total Private + Common)
If instead you divide the shared area in proportion to room size, the common space cancels out and the split is simply each room’s share of the private square footage:
Share = Rent * Private / Total Private
Variables:
- Rent is the total monthly rent for the unit
- Private is the square footage of one roommate’s private bedroom
- Total Private is the sum of every private bedroom’s square footage
- Common is the shared square footage (living room, kitchen, hallways)
- n is the number of roommates
The default assumes equal use of shared space. You can instead allocate it in proportion to private room area. Unrounded shares sum to the full rent. The calculator rounds down to cents and assigns remaining cents to the largest fractional remainders, using room order for ties, so displayed shares also sum exactly.
Example Split for a Three-Bedroom
Suppose the rent is $2,400, the three bedrooms measure 120, 110, and 150 square feet, and 600 square feet of common space is split evenly. The table shows each roommate’s effective area and monthly share.
| Roommate | Private room | + Shared (600/3) | Share of rent | Monthly |
|---|---|---|---|---|
| A | 120 sq ft | 320 sq ft | 32.7% | $783.67 |
| B | 110 sq ft | 310 sq ft | 31.6% | $759.19 |
| C | 150 sq ft | 350 sq ft | 35.7% | $857.14 |
| Total | 380 sq ft | 980 sq ft | 100% | $2,400.00 |
The roommate with the largest bedroom pays the most, but because the shared space is divided equally the gap stays modest. You can still adjust by hand for perks like a private bathroom or a balcony.
Example Problems
Example 1: Two roommates, no shared area entered.
Rent is $1,600 and the bedrooms are 200 and 150 square feet. With no common area, each share is just the room’s fraction of the 350 total: the larger room pays 1,600 * 200 / 350 = $914.29 and the smaller pays 1,600 * 150 / 350 = $685.71.
Example 2: Adding shared space evenly.
Using the same two rooms with 300 square feet of shared space split evenly, each person gains 150 square feet. The larger room’s effective area is 350 and the total is 650, so its share is 1,600 * 350 / 650 = $861.54 and the smaller room pays $738.46. Sharing the common space evenly narrows the difference between the two.
Frequently Asked Questions
Is it fair to split rent by room size?
It is one possible starting point when roommates agree to use private bedroom area. Dividing shared area equally assumes equal access and use; it does not establish what is fair for every household. Many roommates then fine-tune for features like an en-suite bathroom, more closet space, or a better view.
Should the living room and kitchen count in the split?
Because shared rooms belong to everyone, the common approach is to divide their square footage equally rather than assign it to one person. This calculator does that by default. If you prefer, you can instead spread shared space in proportion to bedroom size. Relative to an equal-shared-area split with positive common area, this increases the share of rooms larger than the average and decreases the share of smaller rooms.
How do we handle a private bathroom or balcony?
Start with the square-footage split, then add a flat premium to the room with the extra perk and subtract it evenly from the others. For example, the roommates might agree that a private bathroom is worth $75 a month; add that to that room’s share and reduce each other share so the total still equals the full rent.
