Rent Split Calculator
Split rent equally or by room weights with an equal common-space share. Whole-cent allocations always add to the entered rent.
Interactive calculator · Method RENTSPLIT-1.0 · Last reviewed: 2026-10-05
Calculate your scenario
For n active roommates, share = rent × [common%/100 ÷ n + (1 − common%/100) × room weight/total room weight]. Set common share to 100% for an equal split, or 0% for room-weight-only. Round rent to cents, floor raw allocations, then distribute remaining cents to the largest fractional remainders; ties use row order.
Your inputs
Default worked example. Edit the inputs to calculate your scenario.
Default worked example
The shares add exactly to $2,400.00 after whole-cent allocation. Zero room weights are unused rows. This is an agreed allocation, not a legal fairness rule.
How to use the calculator
Enter total monthly rent to whole cents. Agree the percentage shared equally, then enter room areas in one unit or agreed positive weights. Set an unused roommate row to zero. Check that the allocated shares sum to rent.
What the result means
With $2,400 rent, half shared equally, and weights of 100 and 150, the two shares are $1,080 and $1,320. Common-space weighting is an editable agreement.
Formula and units
For n active roommates, share = rent × [common%/100 ÷ n + (1 − common%/100) × room weight/total room weight]. Set common share to 100% for an equal split, or 0% for room-weight-only. Enter rent in whole cents, floor raw allocations, then distribute remaining cents to the largest fractional remainders; ties use row order.
Worked examples
Two rooms, half split equally: Total monthly rent: 2400 USD; Share split equally: 50 %; Roommate 1 room weight: 100 same-unit area or weight; Roommate 2 room weight: 150 same-unit area or weight; Roommate 3 room weight (0 = unused): 0 same-unit area or weight.
Example result: Roommate 1 monthly share: $1,080.00; Roommate 2 monthly share: $1,320.00; Roommate 3 monthly share: Unused row; Allocated monthly rent: $2,400.00; Common share agreement: 50%.
Three roommates sharing equally: Total monthly rent: 1000 USD; Share split equally: 100 %; Roommate 1 room weight: 1 same-unit area or weight; Roommate 2 room weight: 1 same-unit area or weight; Roommate 3 room weight (0 = unused): 1 same-unit area or weight.
Example result: Roommate 1 monthly share: $333.34; Roommate 2 monthly share: $333.33; Roommate 3 monthly share: $333.33; Allocated monthly rent: $1,000.00; Common share agreement: 100%.
Limitations and common mistakes
Room weights must use one consistent unit. Two or three positive weights activate roommates; zero means unused. The method is an agreed allocation, not a legal or objective fairness standard. Utilities, deposits and lease responsibilities are excluded.
Room weights must use one comparable basis. The equal-share percentage applies to total rent, not to an additional charge on top of it.
Sources and assumptions
Method RENTSPLIT-1.0; last formula review 2026-10-05. Sources and their supported claims. Calculation methodology.