Splitting rent when the rooms aren’t equal

The “just divide by the number of roommates” approach works only when the rooms actually are equal. They almost never are. Here’s a real method for dividing rent fairly, plus how to handle the other monthly costs nobody agrees on.

You found an apartment. It has a master bedroom with a private bathroom, a decent middle room with a closet, and a small room right off the kitchen with no closet at all. Total rent is $3,600/month. If three roommates split that evenly, everyone pays $1,200. The person in the tiny room near the kitchen is getting the worst deal of their life.

There is a better way. It has a name (the “Sperner method,” after a famous economics game), a free web tool at The New York Times’ rent calculator, and a simpler version you can do at the kitchen table in 15 minutes.

The envelope method

Everyone writes down, privately, what they’d be willing to pay for each room — as if they were bidding. The numbers don’t have to add up to the rent; they just have to reflect what each person values each room at.

Example for that same $3,600 apartment:

Now: assign each person the room where their bid is highest relative to the others. Jess bid highest on the master, Marco on the middle and the small room, Priya in the middle of everything. The algorithm gives Jess the master, Priya the middle, and Marco the small room.

Now scale the bids so they sum to $3,600. Jess ends up paying $1,420, Priya $1,110, Marco $1,070. Everyone is paying less than they bid for their room, and more than they bid for the rooms they didn’t get. This is the property the method guarantees: envy-free. No one would rather swap their room and rent for anyone else’s.

If you don’t want to run the math yourself, use the NYT calculator linked above. It takes two minutes.

When the envelope method is overkill

If the rooms really are similar — same size, same sunlight, same distance to the bathroom — just split evenly. If two rooms are roughly equal and one is noticeably bigger, use a simple square-footage ratio. A 120 sq ft room vs. 180 sq ft rooms in an apartment with 480 total sq ft of bedroom space? The small room pays (120/480) × total rent.

Utilities, Wi-Fi, and the shared stuff

Most roommate spreadsheets fail at the utility bills, not the rent. Some principles that work:

• Wi-Fi, streaming, water: Split evenly. Everyone uses them the same amount, practically speaking.
• Electricity and gas: Also split evenly unless one person runs a space heater 24/7 or sets the thermostat to 77°F in summer. Worth a conversation, not a spreadsheet.
• Cleaning supplies, paper towels, kitchen staples: Rotate who buys them. Whoever bought last doesn’t buy again until the others have caught up.
• Groceries:Generally do not share. Even friends who split food run into conflict. “Why did you eat my yogurt” is the top cause of roommate tension.

Move-in costs

The first month of rent, last month of rent, security deposit, broker fee, cleaning fee, and furniture purchases should be split the same way as monthly rent — proportionally by room. If the broker fee is $3,600 and Jess is paying 39.4% of the rent, Jess pays 39.4% of the broker fee.

Security deposit is the trickiest. It’s refundable (in theory), so track who put in what and refund proportionally when the lease ends. Don’t mix security deposit money with rent — it causes confusion three years later.

When someone moves out mid-lease

You need a new roommate fast. The rent split might change. Two rules help:

1. The new roommate inherits the room, not the rent. Re-bid on the rooms if the old roommate’s rent no longer reflects the new group’s preferences.
2. Return the outgoing roommate’s share of the deposit from your own pockets, not from the landlord. You’ll settle up with the landlord at the end of the lease. Otherwise the incoming roommate has to pay the deposit twice.

Tools worth using

Use a shared tracker for month-to-month expenses. Many roommates use Splitwise for this. For restaurants and group dinners specifically, splitmaxis faster — scan the receipt, split by item, pay through Venmo or Cash App. The two tools don’t overlap much: Splitwise is good for ongoing IOU tracking; splitmax is for the moment you’re actually at the table with a bill.

For dinners with a big group of roommates or friends, see our guide to itemized restaurant splits — the fairness logic is the same, just at a smaller scale.