Rent Split Calculator

How this calculator decides what is fair

Most roommates default to one of two methods, and both of them are unfair in predictable ways.

Splitting the rent equally means the person in the tiny back bedroom with no closet subsidizes the person in the primary suite with the private bathroom. Splitting purely by square footage overcorrects in the other direction, because everyone uses the kitchen, the living room, the laundry and the yard exactly the same amount no matter how big their bedroom is.

This calculator uses a practical two-pool method. It is a negotiation aid, not a published industry standard.

• The private pool (default 60% of rent) pays for the bedrooms. It is divided in proportion to each room's value, weighing size first and then bathroom access, closet, natural light, parking, furnishing and floor level.
• The shared pool (default 40% of rent) pays for the common areas. It is divided equally by headcount, because a person is a person regardless of which bedroom they sleep in.

Utilities, if you enter them, are always divided by headcount rather than by room. Two people in one bedroom run two showers and charge two laptops.

What each adjustment is worth

These multipliers apply to the private pool only. They reflect the premiums commonly seen in shared-housing listings, but they are starting points, not laws of nature.

How to actually have this conversation

The number is the easy part. Presenting it is where people get stuck. A few things that work:

• Show the method before the number. If people agree the method is fair, they rarely fight the output. Walk through the two pools first, then reveal the amounts.
• Let them adjust the inputs themselves. Hand over the calculator. Someone who moves the sliders and gets a similar answer stops feeling like the number was imposed on them.
• Agree on a review date. "Let's revisit this in six months, or if someone moves out" removes the sense that this is permanent and unchallengeable.
• Write it down the same day. The agreement is not the paperwork, but the paperwork is what you will both rely on in nine months when nobody remembers what was said.

If you are the live-in homeowner, read this part

This calculator assumes a fixed total rent being divided among housemates. If you own the home and are renting out a spare room, your situation is different in two important ways.

First, you are not dividing a rent payment, you are setting a price. Your mortgage payment is not the right anchor, because your mortgage builds your equity and includes property taxes and insurance that a tenant is not renting. Price the room against comparable rooms in your area, not against your own costs.

Second, you keep exclusive use of far more of the home than a typical housemate does. If you have the primary suite, a home office and the garage, your housemate is not getting an equal share of the property and should not be charged as if they were.

A reasonable approach for homeowners: use this tool to sanity-check that what you are charging is proportionate to what you are actually providing, then confirm the number against local market data.

Read the full guide to pricing a spare room →

Common questions

Should a couple sharing one bedroom pay more?

Usually yes, but not double. Enter 2 occupants for their room and the calculator handles it correctly: they pay one room-based amount for the bedroom itself, but two headcount shares of the common space and utilities. That reflects reality, because two people in one room use the same bedroom but two people's worth of kitchen, bathroom, hot water and electricity.

What if one person got there first and has been paying less?

Seniority is a real consideration but it is not a math problem, it is a negotiation. One common compromise is to calculate the fair split, then phase the existing housemate up to it over two or three months rather than changing it overnight. Another is to let the longest-tenured person have first claim on the best room when one opens up, rather than a permanent discount.

Should the person with a home office pay more?

If they have exclusive use of an additional room, yes. The cleanest way to handle it is to add the office's square footage to that person's bedroom, so a 130 sq ft bedroom plus a 90 sq ft private office becomes a single 220 sq ft entry. That charges them proportionally for the extra private space without breaking the headcount math. If everyone shares the office, leave it out entirely and let it be absorbed by the common-space pool.

Does this account for who uses more utilities?

It divides utilities by headcount, which is the standard and least contentious approach. Metering individual usage in a shared home is impractical and tends to create more conflict than it resolves. If one person genuinely runs a space heater around the clock or works from home while everyone else is at an office, handle that as a flat monthly adjustment agreed between you rather than trying to model it.

Is any of this legally binding?

No. This is a math tool, not a legal document. What makes a rent arrangement enforceable is a written agreement signed by the parties, and in many situations a lease or room rental agreement that complies with your state's landlord-tenant law. Use the number this produces as the input to that document, not as a substitute for it.