Three unequal bedrooms, one rent
When the biggest room is almost twice the smallest, an equal split means the small room quietly pays for the big one. Weighting by floor area fixes that in a way everyone can check.
Kitchen, living room, shared bath. The rest of the rent follows each room.
Closet, light, noise
Closet, light, noise
Closet, light, noise
Weights you agree on
The link holds the whole split. Nothing is stored on our server until you make it a household.
The working, room by room
| Room | People | Weight | Shared part | Room part | Pays |
|---|---|---|---|---|---|
| Large | 1 | 190 × 1 | $480.00 | $943.45 | $1,423.45 |
| Medium | 1 | 140 × 1 | $480.00 | $695.17 | $1,175.17 |
| Small | 1 | 105 × 1 | $480.00 | $521.38 | $1,001.38 |
| Total | 3 | $1,440.00 | $2,160.00 | $3,600.00 |
Weight = floor area × the room’s multiplier (private bath and factors). Unrounded parts are shown; the “Pays” column is rounded to cents so it adds up exactly.
The numbers, step by step
Three roommates rent a $3,600 three-bedroom. The rooms are 190, 140 and 105 sq ft with no private baths. 40% of the rent covers the living room, kitchen and bathroom and is split evenly; the other 60% follows each room’s floor area.
- Large pays $1,423.45: 1.31× average floor area.
- Medium pays $1,175.17: 0.97× average floor area.
- Small pays $1,001.38: 0.72× average floor area.
- Total: $3,600.00, exactly the rent.
Names and amounts are samples. Change any number in the calculator above and the result updates.
A fairness test you can run together
Fair-division research calls a split envy-free when each person feels they got the best piece “in her own estimation”, as Francis Su puts it. Ask: at these prices, would anyone rather swap rooms? If not, nobody envies anyone. Bid mode makes that a guarantee.
Keep it running
Turn this into a household: rent posts at the agreed split each month, bills split by days home, and housr works out who owes whom. Roommates join with a link and a name.
Make it a householdWhen this split is fair, and when it isn’t
Fair when
- The rooms differ mostly in size, and size is what people will notice every day.
- Measurements are taken the same way for every room (wall to wall, excluding closets, or including them for all).
- Everyone sees the same table, so the person in the small room knows exactly what they’re saving and why.
Not so fair when
- If the small room has the best light or the quietest wall, size alone undervalues it; add the light or noise factor.
- If the large room is large because it’s also a walkway (people pass through to the balcony), discount its area.
- If people value the rooms very differently, bidding (envy-free) gives a result that size weights can’t.
This is general information about splitting costs between yourselves, not legal advice. Your lease and your state’s law decide what you owe the landlord.
Sources
- Spliddit, Assign Rooms and Share Rent. Checked 2026-10-05.
- Gal, Mash, Procaccia and Zick, Which Is the Fairest (Rent Division) of Them All? (J. ACM 64(6), 2017). Checked 2026-10-05.
- Francis Su, Harvey Mudd College, Fair Division Calculator (historical page). Checked 2026-10-05.
Related situations
Bid for rooms so nobody wants to swap
Instead of arguing about what a bath or a window is worth, each person puts a price on each room. The result gives every room to someone who values it, at prices nobody envies.
Open the example Split rentOne room has no window. How much less should it pay?
Daylight changes how a room feels to live in, and most people would pay more for it. Give it an explicit weight instead of a vague discount.
Open the example Split rentFour friends, three bedrooms, one shared room
Two people sharing the big room give up privacy, but they also get the most space. The hybrid split prices both: they pay per head for the shared rooms and half the big room each.
Open the example