Rent Proportion Calculator
When roommates pay different amounts, the fairest split is proportional: each person pays in proportion to what they get or what they earn. This calculator splits rent three ways: equally, by bedroom size (with an adjustment for a private bathroom), or by income. Add shared utilities and you get a complete per-person monthly total you can all agree on in writing. It is pre-filled with the room-size example from this article, so click Split Rent to see it work.
Household total: /month
| Roommate | Basis | Share | Rent | Utilities | Total / month |
|---|---|---|---|---|---|
| Totals | |||||
Quick Answer
Three roommates, $2,400 rent, bedrooms of 200, 150, and 120 sq ft: by room size the shares are $1,021.28, $765.96, and $612.76. The calculator above is pre-filled with exactly this example: click Split Rent to see it, then switch the method to compare equal and income splits on the same rent.
Key takeaways
- Equal split is only fair when rooms are genuinely equivalent. When rooms differ, proportional splits stop the small-room roommate subsidizing the big room.
- Room-size shares use private bedroom area only. A private bathroom adds 10% weight to that room in this calculator.
- Utilities are split equally here, whatever rent method you pick. If one person works from home full time, agree a different utility rule in writing.
- Shares are rounded to the cent and any remainder goes to the last person, so the table always adds up to exactly the rent.
The three ways to split rent proportionally
Short answer: equal divides by headcount, room size divides by private space, and income divides by earnings. The right one is the one that matches what actually differs in your place.
1. Equal split
Each person pays total rent divided by the number of roommates. Simple and defensible when rooms are similar in size and quality, and it has one underrated virtue: nobody pulls out a tape measure. Use it when bedrooms are roughly the same, everyone uses shared rooms about equally, and incomes are in a similar ballpark.
2. By room size
Each person pays in proportion to their private bedroom area. Each share equals total rent times (room size divided by total room size). A private bathroom gets a 10% weight bump in the calculator, reflecting the real value of not sharing. That 10% sits at the low end of the 10 to 15% bathroom premium other guides quote, which keeps it defensible rather than punitive. Common areas are handled implicitly: everyone pays only for private space while the whole rent is divided, which is the simplest proportional method and the one most roommate tools use. The shared-space alternative is covered honestly in its own section below, because it gives different numbers.
3. By income
Each person pays in proportion to their earnings. Each share equals total rent times (personal income divided by combined income). Higher earners pay more, which keeps housing affordable for everyone, but it requires transparency about pay that not every household is comfortable with. Use the same income basis for everyone, gross or take-home, and revisit the split if anyone's income changes a lot. If income is the only method you need, with more roommates and separate expense categories, the split rent by income calculator goes deeper on that one method.
| Pick this method when | Watch out for |
|---|---|
| Equal: rooms and perks are close to identical | A master bedroom with a bath paying the same as a box room breeds resentment fast |
| Room size: bedrooms clearly differ, incomes are private | Measure bedrooms only, and agree how closets and balconies count before you measure |
| Income: earnings differ a lot and everyone agrees to share figures | Income splits need re-running after a raise, a job loss, or a new roommate |
Worked examples, checked against the calculator
Short answer: the same $2,400 rent gives three very different tables depending on the method, and the calculator reproduces every figure below to the cent.
By room size: three roommates, $2,400 rent, bedrooms of 200, 150, and 120 sq ft (470 total). Person A: 200 divided by 470 times $2,400 equals $1,021.28. Person B: 150 divided by 470 times $2,400 equals $765.96. Person C: 120 divided by 470 times $2,400 equals $612.76, with one cent adjusted so the shares sum to exactly $2,400. Add $180 of utilities split equally at $60 each and the monthly totals become $1,081.28, $825.96, and $672.76.
By income: three roommates, $2,400 rent, monthly incomes of $5,000, $3,000, and $2,000 ($10,000 combined). Person A: 50% times $2,400 equals $1,200. Person B: 30% times $2,400 equals $720. Person C: 20% times $2,400 equals $480. With the same $180 utilities at $60 each, the totals become $1,260, $780, and $540.
Equal: the same $2,400 rent split three ways is $800 each, plus $60 utilities, for $860 each. Compare that with the room-size table: the person in the 120 sq ft room pays $187.24 a month less than the equal split, and the person in the 200 sq ft room pays $221.28 more. That gap is the whole argument for proportional splits, stated in dollars.
The shared-space question, answered honestly
Short answer: this calculator divides the whole rent by private-space weights, while some guides first carve out a shared-space portion and split that evenly. Both are defensible, they give different numbers, and your household should pick one on purpose.
Take the same rooms, 200, 150, and 120 sq ft, and $2,400 rent. The whole-rent method above gives $1,021.28, $765.96, and $612.76. A carve-out method that assigns 40% of the rent ($960) to shared space, split evenly at $320 each, and divides the remaining $1,440 by room size gives $932.77, $779.57, and $687.66. The carve-out softens the differences: the big room pays about $88 less and the small room pays about $75 more than under the whole-rent method. Neither answer is "the" fair split. The whole-rent method is simpler and needs no shared percentage to argue about; the carve-out method reflects the fact that everyone uses the kitchen and living room equally. If your household prefers the carve-out, agree the shared percentage first, then run the two parts through this calculator as separate calculations and add them. What you must not do is mix methods mid-year without telling anyone: pick one, write it down, and stick to it until everyone agrees to change it.
Put the agreement in writing
Short answer: math prevents most roommate money fights, but only if everyone agrees to the numbers upfront and signs them.
- Record the method and the inputs: total rent, split method, each room size or income used, the utility rule, and the resulting shares. The copy button above gives you a clean summary to paste into the agreement or a group chat.
- Cover move-outs before anyone moves in: who covers the gap until a replacement is found, and how much notice a departing roommate owes. Common approaches: the departing roommate pays until a replacement is found, or the remaining roommates absorb the cost and split it by the same method.
- Handle mid-month moves by days, not by months: split by days, not by the calendar month. Daily rent equals monthly rent divided by days in the month; days with fewer roommates are paid by whoever was actually there, and shared days use your normal ratio. Splitting a whole month evenly when one person arrived on the 16th overcharges them for two weeks they did not live there.
- Remember the lease still rules: co-tenants are generally each liable to the landlord for the full rent, whatever your internal split says. Your agreement divides the bill between yourselves; it does not change what the landlord can collect. If one roommate does not pay, the others still owe the landlord the whole amount.
Two affordability checks belong before you sign anything. First, what rent can the household actually carry: the ideal rent calculator works from income to a sustainable rent figure. Second, what landlords test: many apply a 40-times-rent income rule, which the 40x rent rule calculator checks for you. A split nobody can afford is not a fair split, whatever the method.
What competing calculators miss
Short answer: the rival splitters compute the same three methods, but they present one answer as the truth, skip the shared-space choice, and leave the agreement to you.
- One method presented as the answer: most rival tools ask you to pick a method and show its table, without showing what the other methods would have charged on the same rent. This page's worked examples put equal, room-size, and income side by side in dollars, so the household can see the trade-off before arguing about it.
- The shared-space choice, hidden: several guides now recommend carving out a shared-space portion, yet their calculators divide the whole rent by room size anyway, or vice versa, without saying which they did. This page names both methods, prices both on the same example, and tells you how to run the carve-out version here.
- Utilities, assumed equal without saying so: rivals typically split utilities evenly by default and stop there. This page says so plainly, and flags the case that breaks the assumption: a roommate working from home full time or running energy-hungry equipment should carry a higher utility share by agreement.
- Move-ins, move-outs, and couples, missing: mid-month proration by days, the move-out gap rule, and the couple compromise (about 1.25 to 1.5 shares for a couple sharing one bedroom, rather than a full double) are absent from the rival tools. All three are covered above because they are where real households actually fight.
- The gap this page fills: three methods with dollar comparisons, the shared-space choice priced both ways, proration and agreement steps, and a copy-ready summary for the written agreement.
Frequently asked questions
There is no single answer, but proportional splits beat flat splits whenever rooms differ. Splitting by room size is the most common fair method; splitting by income is fairer on affordability but requires sharing salary information. Equal splits are only fair when rooms are genuinely equivalent.
Yes, under any proportional method. If one bedroom is twice the size of another, paying the same amount means the person in the smaller room subsidizes the larger one. The room-size method in the calculator handles this automatically, with a 10% weight bump for a private bathroom.
Most households split utilities equally, since everyone uses heat, water, and internet. This calculator does exactly that. If one roommate works from home full time or runs energy-hungry equipment, consider weighting their utility share higher by agreement.
Your written agreement should say who covers the gap. Common approaches: the departing roommate pays until a replacement is found, or the remaining roommates absorb the cost and split it by the same method. Decide this before anyone moves in.
Usually yes for shared costs. A common compromise is that a couple pays about 1.25 to 1.5 shares of the per-person amount rather than a full double, since they share one bedroom. Put whatever you agree on in writing.
Re-run the split with the new figures and agree the change in writing before it takes effect. Income splits only stay fair while the incomes behind them are current, so a raise, a job loss, or a switch to part-time work is a reason to recalculate, not to keep paying last year's shares.
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References
- Carelon Wellbeing (Home Depot Employee Assistance Program). Renting a House or Apartment With Roommates (co-tenants may split rent unequally between themselves, but each remains independently liable to the landlord for all of the rent). Accessed October 26, 2026.
- Nolo. Roommates (roommate agreements, deposits, and what happens when a roommate leaves). Accessed October 26, 2026.
- Yukon Residential Tenancies Office, via Tenant Rights Canada. Roommates and Shared Housing in Yukon: Tenant Guide (written roommate agreements should list each person's rent amount and how utilities are split, and remaining tenants may still owe the full rent after a move-out). Accessed October 26, 2026.
- LegalClarity. How to Pay Rent With Roommates: Fair Splits and Risks (proportional splits by bedroom share of private space, and private-bathroom and view premiums on top of square footage). Accessed October 26, 2026.
- Wikipedia contributors. Roommate (background on shared-housing arrangements; used for terminology only, not as the source for any formula). Accessed October 26, 2026.