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How to calculate prorated rent and split the bills when a roommate moves out

Published October 12, 2026 by the developer of SplitWithUs (about)

When a roommate moves out partway through a lease, the money rarely ends on the day the boxes leave. There is the last month's rent, utility bills that arrive weeks later, a deposit the landlord may still be holding, and a sofa or a TV that was bought together. Each one has a reasonable way to split it, and none of them is hard on its own. The trouble is doing all four at once without anyone paying twice. This guide goes through each part and then settles one move-out from start to finish.

How to calculate prorated rent

Prorated rent is rent for part of a period. The usual way to work it out is the daily rate: divide the rent by the number of days the period covers, then multiply by the days the person lived there. Count both the first and the last day, the same way the bill counts its own period. A bill for October 1 to 31 covers 31 days; one for September 1 to 30 covers 30.

Example. Rent is $1,800.00 for October 1 to 31, and the tenant moves out on October 18, so they lived there 18 days. Daily rate: $1,800.00 ÷ 31 days = $58.06 a day, rounded. Prorated rent: $1,800.00 × 18 ÷ 31 = $1,045.16. Rounding the daily rate first and then multiplying gives $1,045.08. The few cents of difference come from rounding too early, so multiply first and round once at the end.

Some leases use a 30-day month for every month, or a yearly rate divided by 365. Neither is more correct than the calendar. Real days make each day of one month cost the same, so a day in February costs more than a day in August. A 30-day month keeps the daily rate the same all year, so whoever leaves in a 31-day month pays for one more day than they would by the calendar. If the lease names a method, it settles the question; if it does not, pick one before anyone works out a number, because each roommate can tell which one suits them.

When the rooms are not the same

Roommates often pay different rent for different rooms. Then the fair way to share the last month is room rent times days lived: each person's weight is their room's monthly rent multiplied by the days they were there. A bigger room pays more for every day it is used.

This raises a question that is easy to miss. What happens to a room that stands empty? If one roommate leaves on the 18th and nobody moves in, the landlord still charges the whole rent, and somebody has to carry those days. There is a fair case on each side:

  • The one leaving pays to the end of the month, or of a notice period. They chose the date, the others did not, and the lease the three of them signed did not shrink. The case is strongest when someone leaves at short notice.
  • The ones staying carry the empty days. They keep the space, and often the empty room becomes a study or storage. The case is strongest when the leaving date was agreed long in advance, or when the others chose not to look for a replacement.
  • A middle way. The one leaving pays until a replacement is found or for a fixed number of days, whichever comes first.

What turns this into an argument is deciding it after the bill arrives, when everyone already knows which answer costs them less.

Utility bills, and the ones that arrive late

Internet, electricity, water and gas are usually split by the days each person lived there, with no difference between rooms. Days lived is a fair proxy, not a measurement. A roommate who ran a heater all winter and one who was away most weekends pay the same per day, and accepting that is simpler than arguing over a meter nobody can split. If one person clearly used much more, say so and agree a fixed extra amount; it is easier than changing the rule.

The catch is timing: the last electricity bill can take a month to arrive. Settling with an estimate is fairer than waiting, because the person leaving may be hard to reach later. A good estimate is last year's bill for the same month, since heating and cooling change the amount more than anything else. Agree that the difference will be settled by the same days when the real bill comes, whichever way it goes.

The deposit

A deposit has two parts to agree on: the deductions, and who pays it back.

  • Deductions. A deduction for a shared space, like cleaning the kitchen, is shared by all the roommates who paid into the deposit. A deduction for one bedroom, like repainting it, belongs to whoever had that room.
  • If everyone moves out, the landlord refunds the deposit, usually to one person, who sends each of the others what they put in less their deductions.
  • If the lease goes on, the landlord keeps the deposit. The roommate taking over the room usually pays the one leaving their part, less any deduction they are expected to have caused, and gets it back from the landlord when the lease finally ends.

Furniture and other shared stuff

Things bought together lose value as they are used, so the price paid is rarely the right number. A simple, open method is straight-line value: the item loses the same amount every month until the end of its expected life, so its worth today is the price minus the months already used. A $600.00 TV expected to last six years has lost a quarter of its value after 18 of its 72 months. Whoever keeps it pays each other owner their share of that value. If the group agrees on another number, because the item is nearly new or badly worn, use that number instead; the formula is a starting point, not a ruling.

One move-out, worked through

Maya, Leo and Sam share an apartment. Their rooms rent for $1,000.00, $900.00 and $800.00 a month. Sam moves out on October 18, Jo moves into Sam's room on October 19, and the lease goes on.

Example. Four parts, all in US dollars. October rent, $2,700.00, paid by Maya, split by room rent and days. Maya $1,000.00 and Leo $900.00; Sam's room is shared by days, Sam 18 days $464.52 and Jo 13 days $335.48. Internet, $62.00 for October, paid by Leo, split by days lived: Maya $20.67, Leo $20.66, Sam $12.00, Jo $8.67. The leftover cent goes to Maya. Deposit, $900.00 from each of the three. Repainting Sam's room is expected to cost $120.00, so Sam's part is $780.00, which Jo pays as the one taking over. TV, $600.00, owned by Leo and Sam, used 18 of its 72 months: worth $450.00. Leo keeps it and owes Sam $225.00. Transfers: Jo sends Maya $1,124.15, Leo sends Maya $555.18, and Leo sends Sam $528.48. Settling each part on its own would take more transfers, and Maya, who paid the rent, would have to pass some of it on.

Sam ends up receiving money even though Sam owes rent and internet: the deposit and the TV are worth more to Sam than Sam's last 18 days cost. Netting the parts together is what makes that visible in one number.

Where move-outs usually go wrong

  • A partner who stayed over a lot. If someone's partner was there most nights, the others may feel the utilities should reflect it. Raise it while the person is still living there, not in the final bill.
  • Things left behind. A desk the leaver does not want is not automatically a gift to the ones staying. Agree whether it is sold, kept at a price or kept for nothing, and if it is sold, who gets the money.
  • Deductions nobody saw coming. A landlord's list can arrive weeks later. Agree in advance that a shared-space deduction is shared even if it lands after someone has left.
  • Settling each part separately. Rent one week, the deposit a month later, the sofa never. Netting everything at once is what keeps the leaver from chasing three small amounts.

How the calculator handles it

The prorated rent calculator for roommates moving out settles the bills, the deposit and the shared stuff in one short list of transfers, and its page shows how to enter a 30-day lease, a late bill or a deposit that has not been refunded yet. It works in one currency; for a trip paid in several, use the trip settle-up. The methodology page lists every rule.

What to watch

  • Read the lease first. It may say how rent is prorated, whether a departing roommate must find a replacement, or how the deposit is returned.
  • Deposit rules and deadlines depend on where you live. This guide shows the arithmetic, not what a landlord may or may not deduct.
  • Take dated photos of your room and the shared spaces when you move in and out; they settle most deposit questions before they start.
  • Small loans between roommates are not shared bills. The guide on when one friend pays for another covers those.

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