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Rent Split by Room Size Calculator

Enter the total rent and each room's area to split rent fairly by size.

How it is calculated

Each person pays in proportion to the area of their own room: share = rent × room area ÷ (A + B + C). Rent is the total monthly amount in money; the room areas can be in any one unit (square feet or square metres) as long as all rooms use the same one, because only the ratio matters. The tool supports up to three rooms. Rooms A and B and the rent must be above zero; room C is optional, and if you leave it empty its share is shown as $0.00 and the rent is split between A and B only. Each share is rounded to cents separately, so the shares can occasionally differ from the rent by a cent. Shared areas such as the kitchen or living room are not weighted separately, they are simply left out of the room areas.

Worked example

The rent is 2,400 and the three bedrooms measure 180, 140 and 100 square feet. Step 1: total area = 180 + 140 + 100 = 420. Step 2: room A pays 2,400 × 180 ÷ 420 = $1,028.57. Step 3: room B pays 2,400 × 140 ÷ 420 = $800.00. Step 4: room C pays 2,400 × 100 ÷ 420 = $571.43. The three shares add back up to the full 2,400.

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Common mistakes

  • Mixing units, for example one room in square feet and another in square metres. The shares are then wrong because only the ratio between the numbers counts.
  • Adding the shared living room or hallway to one person's room area. Entering it for only one room makes that person pay for space everyone uses.
  • Leaving room C empty for a three-person flat. The tool then splits the whole rent between two rooms and shows $0.00 for the third.
  • Expecting the split to reflect a private bathroom, balcony or better light. Only floor area is used, so any such premium has to be negotiated separately.
  • Entering room A as zero or leaving it blank. The tool then gives no result because both of the first two rooms are required.

About this calculator

Splitting rent evenly among roommates ignores the fact that rooms are rarely the same size, so this calculator instead divides the total rent proportionally by each room's square footage: each roommate's share equals (their room's area ÷ total area of all rooms) × total rent. A tenant with a 200 sq ft room in a 600 sq ft three-bedroom apartment would pay one-third of the rent, while someone in a smaller 100 sq ft room pays proportionally less.

This area-based method is one of the most commonly recommended approaches (alongside the “bedroom fairness” and “market-rate” methods) for roommates negotiating a lease, since it's transparent, easy to justify with a tape measure, and avoids arguments about who “deserves” the bigger room.

New roommates signing a shared lease, landlords helping tenants split a master invoice, and subletters use it to agree on a fair number before move-in day, entering the total rent and each room's dimensions or area to get an itemized split.

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Comments (1)

  • Editorial team

    The split looks only at the floor area you enter, so it will not know that one room has a private bathroom, a balcony or more sun. If flatmates feel that matters, agree a fixed extra amount first, subtract it from the rent, and enter only what is left. Rounding is per room, so the three shares can be a cent off the total. How does your household treat a room with its own bathroom?

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