Roommate Cost Split
Name, then what that room is worth, then optionally the day they moved in and the day they moved out: Priya, 520, 2025-10-27. Dates go year-month-day, and anyone without them is charged for the whole period. Put the same number against every name if all the rooms are alike.
What each person owes
$20,800.00 shared out
291 days, 1,029 of them lived in. An equal split would charge everybody $5,200.00.
- Sam$6,904.20 · $1,704.20 more than equal
- Alex$5,704.36 · $504.36 more than equal
- Priya$4,841.83 · $358.17 less than equal
- Jordan$3,349.61 · $1,850.39 less than equal
Where each share comes from
| Person | Days | Rent | Bills | Owed |
|---|---|---|---|---|
| Sam | 291 | $5,999.24 | $904.96 | $6,904.20 |
| Alex | 291 | $4,799.40 | $904.96 | $5,704.36 |
| Priya | 247 | $4,073.71 | $768.12 | $4,841.83 |
| Jordan | 200 | $2,727.65 | $621.96 | $3,349.61 |
| Handed out | 1,029 | $17,600.00 | $3,200.00 | $20,800.00 |
Rent is divided by room rate multiplied by days, and bills by days alone. That second rule is deliberate: a boiler, a router and a fridge serve the flat rather than a bedroom, so charging the person with the box room a smaller share of the heating has no argument behind it. What the rooms are worth is your judgement, not this page’s — a rate is a weight, and only the ratios between them change the answer.
The shares are worked out to the smallest unit of money and always add back to the total exactly. Nothing is rounded on its own and left to drift, because a split where four people each pay a rounded share and the landlord ends up owed a little more is precisely the kind of small wrongness that costs an evening to argue about.
The worked examples below are in US dollars. The tool itself works in whichever currency you pick above, and never converts between them — what you type is what it does the arithmetic on.
Equal is the default, and it is usually wrong
Four people sign one tenancy and what follows is nearly always the same sum: the total, divided by four, posted in the group chat, settled by Tuesday. It is fast and transparent, and it charges whoever took the box room over the stairs precisely what it charges whoever took the double with the bay window. It bills a full year to someone whose course did not start until the end of October. Both are transfers from the person least willing to argue to the person most willing, and neither appears anywhere in the sum.
The alternative is not complicated, only tedious by hand: value each room against the others, count the days each person actually had, and hand out the money in proportion. That is what happens here, with the equal share printed alongside so the size of the transfer is visible rather than assumed.
A worked flat: four rooms, four different tenancies
The period runs from 13 September to 30 June — 291 days. Rent for all of it is $17,600 and bills come to $3,200. Sam has the large room, valued at 650; Alex and Priya have the middle pair at 520 each; Jordan has the small one at 430. Priya arrives on 27 October, giving her 247 days; Jordan moves out at the end of March, giving him 200.
Split by heads, all four pay $5,200. Weighted by room and by day, Sam pays $6,904.20, Alex $5,704.36, Priya $4,841.83 and Jordan $3,349.61. That is a spread of more than $3,500, and none of it is new money: every cent was in the equal split too, paid by Jordan and Priya on Sam’s behalf.
Rent and bills are shared on different bases
Rent buys a particular room, so it is divided by room rate multiplied by days occupied. Both halves matter: a dearer room raises the share, and so does being there longer, which is what makes a partial stay come out right instead of being waved through as a rounding decision.
Bills buy the flat rather than a bedroom. The boiler, the router, the fridge and the water serve everyone regardless of which door they sleep behind, so bills are divided by days alone. There is no serious argument for charging the small-room occupant less for heating, and any attempt to build one collapses the moment somebody works from home in February.
Where the missing cent comes from
A thousand dollars between three people is $333.3333 each. Round each share on its own and you collect $999.99 or $1,000.02 depending on which way each one went, leaving whoever pays the landlord short or holding money that belongs to nobody. Repeated monthly, that becomes the kind of small wrongness which eats an evening.
This splitter works in whole cents. Every share is floored, and the leftover cents go one apiece to the shares with the largest discarded fraction. Three people splitting a thousand are charged $333.34, $333.33 and $333.33, which adds back to exactly a thousand: the column of shares always equals the bill you were sent.
What arithmetic cannot settle for you
The room rates are a judgement, and they are yours. If the landlord priced the rooms separately, use those figures. If not, the method that survives contact with housemates is a sealed bid before anyone has moved in: everyone writes down what they would pay for each room, and the numbers are compared while nobody has anything to lose yet.
Outside the split entirely: deposits, damage, and who is liable when a housemate stops paying. Most shared tenancies are joint and several, meaning the landlord may pursue any one of you for all of it, and no division of the rent changes that.
Room values, couples and weekends away
How do we decide what each room is worth?
Only the ratios matter, so you can use monthly figures, weekly ones or a scale of one to ten. Sealed bids before move-in work better than a discussion afterwards, because nobody yet knows which room they will end up defending.
Somebody is leaving early and a replacement is taking the room. How do we enter that?
As two lines with the same room rate: the first person with a move-out date, the second with a move-in date on the following day. Each is then charged for the days they held the room, and the room itself is paid for continuously.
What if two of us share one room as a couple?
Enter them as two lines carrying half the room rate each. Rent then comes out the same as one person paying the full rate, while bills — which are shared by days — correctly count two people using the heating and the hot water.
Someone goes home most weekends. Should that reduce their share?
Not by these rules, and probably not at all. Their possessions occupy the room and it cannot be let to anyone else, so the rent runs regardless. Move-in and move-out dates are for the days a room genuinely changes hands, not for absences.