acalculator

How should our rent split work?

Type the monthly rent and choose how to share it. By room size, each person pays for their own bedroom and an equal part of the shared space, all at the same rent per square foot. By income, each pays the same percent of what they earn.

Your numbers

Split
Bedroom sizes
Row 1
Row 2
Row 3
Who pays what
Person 1: $880.00; Person 2: $792.73; Person 3: $727.27

For $2,400.00 a month: Person 1: $880.00; Person 2: $792.73; Person 3: $727.27.

Highest share
$880.00
Lowest share
$727.27
Shared space
670
Rent per unit of area
$2.18

Who pays what: Person 1: $880.00; Person 2: $792.73; Person 3: $727.27. For $2,400.00 a month: Person 1: $880.00; Person 2: $792.73; Person 3: $727.27.

How to calculate

A rent split calculator for roommates: shares the rent by bedroom size with the shared space split evenly, by income, or evenly.

Example with the default inputs (Monthly rent $2,400.00, Split By room size, Whole home size 1,100, Bedroom sizes [Room size 180; Room size 140; Room size 110]): For $2,400.00 a month: Person 1: $880.00; Person 2: $792.73; Person 3: $727.27.

Method: By room size: share = rent × (own room + (home − all rooms) ÷ people) ÷ home; by income: share = rent × income ÷ all incomes; evenly: rent ÷ people.

  • By room size, every square foot costs the same and the shared space (kitchen, living room, halls) is split evenly.
  • Shares are shown to the cent, so the shown shares can differ from the rent by a cent.
  • Bathrooms, parking or a balcony used by one person are not priced separately.

Machine-readable copies: Markdown, JSON.

Worked examples

Each example is checked against the calculator on every build.

  1. Monthly rent $2,400.00, Split By room size, Whole home size 1,100, Bedroom sizes 180; 140; 110 gives Who pays what Person 1: $880.00; Person 2: $792.73; Person 3: $727.27, Shared space 670, Highest share $880.00, Lowest share $727.27.Source: FairSplit, The Room Size Rent Splitting Method (common space split equally, private space split by each bedroom’s share of the square footage), https://usefairsplit.com/guides/how-to-split-rent-by-room-size/ (retrieved 2026-10-03)
  2. Monthly rent $2,400.00, Split By income, Incomes 60000; 45000; 30000 gives Who pays what Person 1: $1,066.67; Person 2: $800.00; Person 3: $533.33, Lowest share $533.33.
  3. Monthly rent $1,850.00, Split Evenly, People 2 gives Who pays what Person 1: $925.00; Person 2: $925.00, Highest share $925.00.

How it works

By room size. With rent R, a whole home of area H, n people and bedrooms of area r₁ … rₙ:

  • shared space S = H − (r₁ + … + rₙ), split evenly: S ÷ n each;
  • share of person k = R × (r_k + S ÷ n) ÷ H.

Every unit of area costs R ÷ H, and the shares add up to R.

By income. With incomes i₁ … iₙ for the same period: share of person k = R × i_k ÷ (i₁ + … + iₙ).

Evenly. Each pays R ÷ n.

Each share is worked out exactly and shown to the cent (half up), so the shown shares can differ from the rent by a cent.

Rules

  • The rent is $0 to $10,000,000; 2 to 20 people.
  • By room size: room sizes are 0 or more, the whole home 1 or more, in any one unit; bedrooms that add up to more than the whole home give no answer.
  • By income: incomes that are all 0 give no answer.
  • This page is one use of the bill split calculator.

Worked examples by hand

$2,400, 1,100 sq ft, bedrooms 180, 140 and 110 sq ft. S = 1,100 − 430 = 670 sq ft; 670 ÷ 3 = 223.33 each. Person 1: 2,400 × 403.33 ÷ 1,100 = $880.00; person 2: 2,400 × 363.33 ÷ 1,100 = $792.73; person 3: 2,400 × 333.33 ÷ 1,100 = $727.27.

$2,400 by incomes of $60,000, $45,000 and $30,000. Total 135,000. Shares 2,400 × 60 ÷ 135 = $1,066.67, 2,400 × 45 ÷ 135 = $800.00, 2,400 × 30 ÷ 135 = $533.33.

$1,850 evenly between 2. $925.00 each.

Other questions people ask

How do you split rent by room size?

Take the whole home’s floor area and subtract the bedrooms to get the shared space, and split that evenly. Each person’s area is their bedroom plus their part of the shared space; their rent is that area ÷ the whole home × the rent.

How much does each roommate pay in the example?

For $2,400 and 1,100 sq ft with bedrooms of 180, 140 and 110 sq ft, the shared space is 670 sq ft, 223.33 each. The shares are $880.00, $792.73 and $727.27, which add up to $2,400.

How do you split rent by income?

Each person pays rent × their income ÷ everyone’s income added up. With incomes of $60,000, $45,000 and $30,000, the shares of $2,400 are $1,066.67, $800.00 and $533.33.

What if I do not know the size of the whole home?

Check the listing or the lease, or measure each room and add a rough figure for the kitchen, living room and halls. Use the same unit, square feet or square meters, everywhere.

Should a room with its own bathroom pay more?

Often, yes. This calculator prices floor area only; you can add an en-suite bathroom’s area to that person’s room size, or agree a fixed amount on top.

How is this related to splitting a bill?

It is one use of the bill split calculator: the rent is a bill shared by the same people every month, split by room size or income instead of by what each person ordered.