# How to split rent by room size (formula and example)

Canonical URL: https://www.evenoutapp.com/guides/how-to-split-rent-by-room-size
Updated: 2026-10-06

Multiply the rent by each bedroom's square footage divided by the total bedroom square footage. First take a share of the rent for common space and split that equally. On $2,700 with 20% common, rooms of 180, 140 and 120 square feet pay $1,063.64, $867.27 and $769.09.

Key points:
- Formula: rent × (bedroom square feet ÷ total bedroom square feet). A $1,800 two-bedroom with rooms of 140 and 100 square feet splits $1,050 and $750.
- Measure length times width of usable floor the same way for every room, and agree up front whether closets, ensuites and sloped ceilings count.
- Take a percentage of the rent for shared space and split it equally. At 0% the rent follows area only, and at 100% it is an equal split.
- In EvenOut, record the shared part as an equal expense and the rest with the Shares split, using square feet as the share numbers.

## What is the formula for splitting rent by room size?

Each person pays the rent times their bedroom's share of the total bedroom area. As a formula, that is rent × (bedroom square feet ÷ total bedroom square feet).

Say a two-bedroom costs $1,800. One bedroom is 140 square feet and the other is 100, so the bedrooms total 240. The rent works out to $1,800 ÷ 240 = $7.50 per square foot, and the rooms pay 140 × $7.50 = $1,050 and 100 × $7.50 = $750. Together that is $1,800. Square meters work the same way, because only the proportions matter.

## How do you measure a bedroom?

Multiply length by width of the floor you can use, and measure every room the same way. A 12 by 15 foot room is 180 square feet, a 10 by 14 foot room is 140, and a 10 by 12 foot room is 120. For an L-shaped room, split it into two rectangles and add them. For other shapes, see [how to calculate room size](https://www.evenoutapp.com/tools/how-to-calculate-room-size).

Settle four questions before anyone picks up the tape:

- **Closets.** A walk-in closet of 4 by 5 feet adds 20 square feet, which turns a 120 square foot room into 140.
- **An ensuite bathroom.** Count it in the room, or leave it out and price it separately.
- **Sloped ceilings.** Decide whether the floor under a low ceiling counts.
- **Walls.** Measure to the inside of the walls for every room, not some to the middle.

Write the numbers where everyone can see them.

## Why take common space out of the rent first?

The living room, kitchen and hallway belong to everyone equally, and a bigger bedroom should not carry a bigger share of them. If you split all of the rent by bedroom area, the largest room pays extra for space that all three people use the same amount.

The fix is a carve-out. Take a percentage of the rent for common space, split it equally, and share the rest by bedroom area. The percentage is a judgment call: at 0% the rent follows bedroom area only, and at 100% it is an equal split. The example below uses 20%.

Take a $2,700 apartment with three bedrooms of 180, 140 and 120 square feet, which total 440. Twenty percent of the rent is $540, so each person pays $180 toward common space. The other $2,160 goes by area.

| Roommate and room | Bedroom part | Common part | Pays |
|---|---|---|---|
| Ana, 180 sq ft | $883.64 | $180.00 | $1,063.64 |
| Ben, 140 sq ft | $687.27 | $180.00 | $867.27 |
| Cy, 120 sq ft | $589.09 | $180.00 | $769.09 |
| Total, 440 sq ft | $2,160.00 | $540.00 | $2,700.00 |

The bedroom part is $2,160 × 180 ÷ 440 for Ana, and the same pattern for the others. Without the carve-out, Ana would pay $2,700 × 180 ÷ 440 = $1,104.55. The 20% common share lowers her rent by $40.91 and raises Cy's from $736.36 to $769.09, which is $32.73 more.

## When is room size the wrong yardstick?

Area says nothing about light, noise, a private bathroom or a walk-in closet. If those matter to your group, add a flat dollar amount for the feature or score each room with points, which [how much more the master bedroom should pay](https://www.evenoutapp.com/guides/how-much-more-should-the-master-bedroom-pay) works through. If the roommates have not yet chosen rooms, [how to decide which roommate gets the bigger room](https://www.evenoutapp.com/guides/how-to-decide-which-roommate-gets-the-bigger-room) covers that conversation. And when the rooms are within a few square feet of each other, an equal split is simpler, as [how to split rent fairly](https://www.evenoutapp.com/guides/how-to-split-rent-fairly) explains.

## How do you record it in EvenOut?

EvenOut's Shares split takes square feet directly, so no conversion is needed.

1. **Create a group of the type Household** ("Rent and bills") and add your roommates.
2. **Add the shared part.** Create an expense for $540.00 called "Rent, shared space", tap the "Paid by you" chip if someone else pays the landlord, and choose Equally in the split picker. Each person owes $180.00.
3. **Add the bedroom part.** Create a second expense for $2,160.00 called "Rent, bedrooms" and choose Shares in the split picker. Type 180, 140 and 120. The sheet shows each person's dollar amount under their name: $883.64, $687.27 and $589.09.
4. **Make both repeat.** Open "Photo, repeat, pending or note" on each expense and choose Repeat, then Monthly. The expense you save is the first one, and EvenOut adds each later one with the same payer and split.

If you prefer a single expense, choose Exact amounts and type $1,063.64, $867.27 and $769.09. That gives one repeat instead of two, but you retype all three amounts whenever the rent changes.

Repeats need a connection to set up and have no end date in the app. When the rent changes, open "Repeating expenses" from the group menu, choose "Stop repeating", and add the new amounts. The square feet stay the same, so only the dollar figures change.

## What should you do next?

Measure the rooms the same way, pick the common percentage, and write both into your roommate agreement. The rent split calculator by room size does the arithmetic for the area part. If three people share a two-bedroom, [how to split rent 3 ways in a 2-bedroom](https://www.evenoutapp.com/guides/how-to-split-rent-3-ways-in-a-2-bedroom) covers the shared room.

## Frequently asked questions

### What if two people share one bedroom?

Work out the room's amount first, then split it between the two people. In the example, the 180 square foot room pays $1,063.64, so two people in it pay $531.82 each. If one of them uses the room more, agree a different split of that amount before you sign.

### Do I need the floor area of the whole apartment?

No. Only the bedrooms go into the formula. Shared space enters as a percentage of the rent that you choose and split equally. The apartment's total floor area can guide that percentage, but you do not have to measure it.

### What happens to the numbers when the rent goes up?

Keep the square feet and the common percentage, and enter the new rent. At $2,850, 20% is $570, or $190 each. The other $2,280 splits $932.73, $725.45 and $621.82, so the rooms pay $1,122.73, $915.45 and $811.82. In EvenOut, stop the old repeats and add the new amounts.