Personal finance · Renting
Roommate rent split, fair to the cent.
Divide one monthly rent by room size, by income or equally, with a fixed premium for a private bathroom or a parking spot. Shares always add up to the rent.
The premiums come off the rent first and are charged only to whoever has the bathroom or the parking. The rest is split by your chosen method. Example: $3,000 rent, rooms of 200, 150 and 120 sq ft, a $150 bathroom premium and a $100 parking premium gives $1,320.21, $977.66 and $702.13.
Inputs
Result
Fill the form and press Split the rent.
Worked example
Three roommates share a $3,000 rent. Alex has a 200 sq ft room with a private bathroom, Bea has 150 sq ft and the parking spot, Cam has 120 sq ft. You agree a $150 bathroom premium and a $100 parking premium, and split the rest by room size.
- Shared rent: $3,000 − $150 − $100 = $2,750.
- Size weights: 200 + 150 + 120 = 470 sq ft. Alex pays 200/470 × $2,750 = $1,170.21, Bea 150/470 = $877.66, Cam 120/470 = $702.13.
- Add the premiums: Alex $1,170.21 + $150 = $1,320.21; Bea $877.66 + $100 = $977.66; Cam $702.13. Total $3,000.00.
Formula and sources
With rent R, bathroom premium b, parking premium p, and a weight wi for each person (1 for an equal split, the room size, or the income):
- Shared rent S = R − (b × rooms with a private bathroom) − (p × rooms with parking)
- Sharei = S × wi / Σw
- Paysi = Sharei + that person's premiums
- Cents: shares are rounded down, then leftover cents go to the largest fractional remainders, so the total equals R exactly.
This is pure arithmetic. It uses no rates, tables or external data, so there is no outside source to cite. The method, formula and rounding rule were written and checked against hand calculations on 1 October 2026. The premiums are numbers you and your roommates agree on, not market prices.
What this does not model
It splits one monthly figure. It does not read your lease, decide who is liable to the landlord, or set a "right" premium. It does not weigh closets, light, noise or furnished rooms; raise the premium for those if you want them counted. When using income, use the same basis (gross or net) for everyone. General arithmetic, not legal or financial advice.
Frequently asked questions
Is splitting rent by room size fair?
It is a common starting point because a bigger room usually carries more of the rent. It ignores things like a private bathroom, a closet, noise or natural light, which is why this tool lets you add a fixed dollar premium for a private bathroom and for parking and then splits the rest by size.
When should roommates split by income instead?
When incomes differ a lot, an equal or size-based split can take a much larger share of one person's pay. An income split makes each person pay the same share of income. It needs everyone to be willing to share their income, so use net or gross consistently for all roommates.
How do the bathroom and parking adjustments work?
The premium is a fixed dollar amount you choose. It is taken off the rent first and charged only to the roommate who has the private bathroom or the parking spot. The remaining rent is then split by your chosen method. There is no standard premium, so pick a number all roommates agree on.
Why do the shares add up exactly to the rent?
Each share is rounded to the cent with the largest-remainder method: every share is rounded down, then the leftover cents go to the shares with the biggest fractional parts. This avoids a one-cent gap that equal splits like 1,000 divided by 3 would otherwise leave.
Does this cover utilities, deposits or what the lease says?
No. It splits one monthly rent figure. Utilities can be split with the same method by entering that bill as the amount. Who is legally liable to the landlord depends on your lease and local tenancy rules, which this tool does not interpret. It is general arithmetic, not legal advice.
General information, not advice
This tool does simple arithmetic on the numbers you enter. Agree the split in writing with your roommates and check your lease for who is responsible to the landlord.