Short answer: split each bill by how many days each person actually lived there. Work out a daily rate for each bill, multiply it by the days each person stayed, and settle up. Rent and fixed bills are simple. Usage bills like electricity take a little more care. Put the whole deal in writing before anyone packs a box.
A mid-month move is messy, a bit like moving house with kids underfoot. The money side doesn't have to be. Here's how to do it step by step.
Step 1: Agree on the move-out and move-in dates
Before you do any math, agree on the exact dates. Things to settle:
- Which day counts as the last day? Is it the day the keys go back, or the day the last box leaves?
- Is someone new moving in? If yes, is there a gap, or do the two overlap?
- Who pays for any empty days? Your lease may already answer this. Many leases hold every tenant on it responsible for the full rent, whether or not a room is empty. Check yours.
Send these dates in a group text or email so everyone has them in writing.
Step 2: Prorate the rent
There are two common ways to work out a daily rate. Pick one and use it for every bill.
Method A: actual days in the month Daily rate = monthly rent ÷ days in that month (28, 29, 30, or 31)
Method B: a flat 30-day month Daily rate = monthly rent ÷ 30
Method A is more exact. Method B is easier to explain. Neither one is wrong, as long as everyone agrees to it.
Hypothetical example
Three roommates share a $2,400 apartment in a 30-day month and split rent evenly, so each share is $800. Sam moves out after day 12. Jordan moves into Sam's room on day 16.
- Sam's daily rate: $800 ÷ 30 = $26.67
- Sam owes: 12 days × $26.67 = $320
- Jordan owes: 15 days (days 16–30) × $26.67 = $400
- Days 13–15 (3 days, $80) are unpaid. The group has to decide who covers them.
If your rooms are different sizes and you pay unequal shares, use each person's own share when you work out their daily rate.
Step 3: Handle fixed bills the same way
Internet, streaming services, renters' tools, and anything else with a flat monthly price can be prorated just like rent:
(monthly bill ÷ days in month) × days in residence ÷ number of people in the home on those days
If that feels like too much for a $60 internet bill, you can also agree that whoever lives there on the 1st pays the whole month. That's fine, as long as you decide it up front.
Step 4: Split usage-based utilities fairly
Electricity, gas, and water change with use, and the billing period often doesn't line up with the calendar month. You have a few options:
- Take a meter reading on move-out day. Photograph the meter with a timestamp. When the bill comes, split the usage before and after that reading.
- Prorate by days in the billing period. Use the dates printed on the bill, not the calendar month.
- Use "person-days." Add up the days each person lived there during the billing period, then divide the bill by that share.
Hypothetical person-day example: A $150 electric bill covers 30 days. Two people were there for all 30 days, and one person was there for 10 days. That's 70 person-days, so the bill works out to $2.14 per person-day. The two full-time roommates each owe about $64.29 and the part-timer owes about $21.43.
Step 5: Don't forget the other shared costs
These are the costs that cause fights later:
- Bills that arrive after move-out. Utilities often bill a month behind. Agree now that the person who left will still pay their share when the bill comes.
- Shared household supplies. Things like toilet paper, cleaning products, and a bulk pantry. Either split the last shared purchase or call it even.
- Furniture and appliances bought together. Decide whether someone buys out the departing roommate's share, and at what price.
- Security deposit. If the landlord keeps one deposit for the whole lease, the new roommate often pays the departing one directly for their share. Deposit rules vary by state and by lease, so read your lease and check your local tenant rules before you agree on anything.
- Cleaning and damage. Walk through the room together and take photos, so no one is surprised when the deposit comes back.
Step 6: Put it in writing and settle up
A short written summary prevents most arguments. Include:
- Move-out and move-in dates
- The method you used (actual days or a 30-day month)
- The amount each person owes for each bill
- How you'll handle bills that haven't arrived yet
- When and how you'll pay (payment app, bank transfer, or cash)
A shared spreadsheet or bill-splitting app makes this easier, especially for bills that trickle in over the next month or two.
Quick checklist
- Dates agreed in writing
- Rent prorated by the same method for everyone
- Fixed bills prorated, or a simple rule agreed
- Meter readings photographed
- Plan for late-arriving bills
- Deposit, furniture, and supplies sorted
- Final amounts confirmed and paid
A roommate change is chaotic, but the math isn't hard. Pick one method, apply it to everyone, and write it down.
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