Alpacto › Tools › Rent split calculator
Rent split calculator: three rules at once, so you can pick one
Most housemates do not argue about the number. They argue about the rule that produced it, and a calculator that hands you one figure without showing its working is no use in that argument. This rent split calculator runs all three common rules side by side and names every coefficient it uses, so you can put the result on the table.
Your rent, room by room
Three rules a rent calculator for roommates can use, and who each one favors
Equal, per person is the rent divided by the number of people, and nothing else. It is the only rule nobody has to trust anybody about, and it is right when the bedrooms are close enough in size that measuring them would be silly. It quietly overcharges whoever took the box room.
By room size takes the common areas off the top and splits them per person, because the kitchen and the sofa belong to everybody equally, then divides what is left in proportion to each bedroom’s floor area. The calculator above takes 30 percent for common areas by default, and that number is a field you can change.
By room size and features works the same way, except a room with its own bathroom carries more weight: 15 percent more by default, again as a field rather than a secret. A balcony and a walk-in closet work the same way, 10 and 5 percent by default. What they are worth is whatever the people living there agree it is worth, so both are fields you change.
What the rent split calculator returns for one real flat
Take the flat the calculator opens with: $2,400 a month, three bedrooms of 180, 130 and 95 square feet, and a private bathroom off the largest one. Split equally, everybody pays $800. By room size the same three people pay $987, $779 and $634, and once the bathroom counts they pay $1,045, $746 and $609.
The big room moves by $245 a month between the first rule and the third. The small room moves by $191 in the other direction, which is $2,292 over a year on a flat nobody has even moved into yet. That is the whole argument, and it is about the rule, not the arithmetic.
Two checks tell you whether any tool here is doing the arithmetic honestly, ours included. Give every room the same floor area and no bathrooms: all three rules should return the same number, and here they return $800 each. Then put two people in one room: they pay two shares of the common areas and one of the bedroom, which turns $800 into $920 for their room and $740 for the others.
Splitting rent by room size: the formula and one worked example
A rent split calculator based on room size gives each person an equal share of the common areas, then divides the rest of the rent in proportion to the floor area of each bedroom. To split rent by square footage in four steps:
- Decide what share of the rent belongs to the common areas. The calculator starts at 30 percent, and you can change it.
- Divide that money by the number of people. Everyone pays this part equally.
- Take the remaining rent and multiply it by your bedroom’s share of the total bedroom area: your square feet divided by everyone’s square feet added together.
- Add the two amounts.
Take $2,400 a month, 25 percent for common areas, and three people in bedrooms of 150, 120 and 90 square feet, 360 in all. The common areas come to $600, which is $200 each.
The other $1,800 splits by area: 150 of 360 is $750, 120 of 360 is $600 and 90 of 360 is $450. The three people pay $950, $800 and $650, and the total is $2,400 again.
Skip the common-area step and divide all $2,400 by area, and the same rooms pay $1,000, $800 and $600. The adjustment moves $50 a month from the biggest room to the smallest, because the kitchen and the sofa belong to everyone equally and do not grow with the size of your bedroom. To check it in the calculator, enter $2,400, 25 percent for common areas and the three areas, then read the “by size” figure; that column ignores the feature boxes.
When to use size alone, and when to add features
Size alone fits when the bedrooms differ in floor area and have about the same fixtures. Add features when one room has something the others lack and its owner uses every day.
A private bathroom is the usual case, and the calculator adds 15 percent to that room’s weight by default. A balcony adds 10 percent and a walk-in closet 5, and you can change all three.
Parking is the exception: the calculator has no field for it, and a space has a price of its own. The simplest way is to agree what the space costs, subtract it from the rent you type in, and let whoever uses it pay that amount on top of their share.
Pick the rule before you move in, not after
Run the same flat through the three rules and the gap is rarely small. A 180 square foot room with its own bathroom and a 95 square foot room without one pay exactly the same under an equal split, and nothing like the same once floor area counts. Whoever is about to lose by a rule will discover a principled objection to it, and they will not be wrong.
That is why the choice belongs at the start, before anybody knows which room they are getting. It is much easier to agree that size should count when you do not yet know whose room is bigger. The same is true of the two coefficients: thirty percent for common areas and fifteen for a bathroom are our defaults, not a standard, and argue about them once, at the start, and never again.
The other half of the job is writing it down. A number agreed in a kitchen at midnight does not survive the third month, and neither does the reasoning behind it. Copy the line the calculator produces, put it where you both see it, and give it a date it starts from.
The tool Google names first asks a different question
Search for this and Google’s own summary puts Spliddit at the top, and it divides nothing you can measure. You give it the roommates, the bedrooms and the monthly total, and it sends everyone a link where they say in dollars what each bedroom is worth to them. Its algorithm then hands out the rooms and the shares together, aiming at what it calls envy-freeness: in its own words, “each roommate feels that they got the best deal”.
That beats anything on this page when nobody has claimed a room yet and the bedrooms are hard to compare. It is the wrong tool once the rooms are taken, because it decides who sleeps where as well as who pays what. One practical thing to know before you type anybody’s name into it: on September 18, 2026 the site answered only over plain http, and the https address did not connect at all.
Rent is the easy part
Rent is one number a month and it is the same every month, which is why it is the thing people calculate. Everything else in a shared flat is smaller, more frequent and much harder to keep even: the groceries, the internet bill, the thing somebody paid for and forgot to mention.
Our shared expenses calculator takes that second list and works out who owes whom at the end of the month. If the question is less about arithmetic and more about who said what, splitting bills in a relationship covers the conversation around it.
Questions people ask
What is the fairest way to split rent?
There is no rule that is fair on its own, which is why this page gives you three and asks you to choose. Equal is fair when the rooms are equal, floor area takes over when they are not, and a bathroom premium covers the case where one person never has to queue. The fairest thing you can do is pick the rule together before anybody claims a room.
How do I split rent by square footage?
Take the common areas off the top first, because nobody owns the kitchen more than anybody else, then divide the rest in proportion to each bedroom. The calculator above uses 30 percent for common areas by default; measure your own place if you want to be exact, and put the real figure in the field. Without that step, a big bedroom pays for a share of the hallway twice.
Can we split rent based on income instead?
You can, and some households do, but it answers a different question: who can afford what, rather than who is getting what. This calculator deliberately stays on the second question, because a room is a thing you can measure and an income is a thing people would rather not compare. If you want the income version, our shared expenses calculator splits costs by pay.
What rent can I afford on a $70,000 salary?
That is a different question, and this page does not answer it. It depends on your income, your debts and your city, none of which a bedroom knows about, and answering it would be financial advice we are not in a position to give. This calculator starts after the rent is agreed with a landlord, and all it decides is who pays which part of it.
Two of us share one room. How does that work?
Set that room to two people. The common areas are then charged per person, so the couple pays two shares of the kitchen and the hallway, while the bedroom itself is charged once as a room. That is the usual arrangement, and we say it out loud because the alternative treatment makes the couple noticeably cheaper and the others notice.
Write the rule down, not just the number
The line this calculator copies out says four things: who pays what, under which rule, with which coefficients, and from which month. Those four survive a disagreement in the way a remembered number does not. A roommate agreement sheet with the same four lines on it is on the way, and it will live in our printables.
What it deliberately leaves alone is everything that is not rent. The deposit, the utilities, the internet and the furniture are separate arguments with separate rules, and folding them into one figure is how a room rent split calculator starts producing numbers nobody can check. It also has no opinion about what your flat should cost, because that is a question about your city and not about your hallway.
When the number is agreed and somebody still forgets
A calculator ends when the arithmetic is done. Alpacto is our own app, and it holds the part that comes next: the agreement itself, signed by both, with what counts as done, by when, and coins that buy rewards you wrote for each other. It is not an accounting app and it does not touch your bank.