The move-out proration formula
Tenant owes = bill ÷ days in period × days occupied × split share. Days are counted inclusive, so a period from September 1 to September 30 has 30 days, and a move-out on September 12 means 12 occupied days.
Worked example: shared water bill
A $180.00 water bill covers September 1 to 30 (30 days). The departing tenant’s RUBS share is 30% and they move out September 10.
| Step | Calculation | Result |
|---|---|---|
| Daily cost | $180.00 ÷ 30 days | $6.00 per day |
| Occupied days | Sept 1 to Sept 10 | 10 days |
| Prorated bill | $6.00 × 10 | $60.00 |
| Tenant share | $60.00 × 30% | $18.00 |
Not sure what share to use? Work it out with the free RUBS calculator, then send the tenant a clear explanation with the bill-back letter generator.
Questions
How do you prorate a utility bill when a tenant moves out?
Count the days in the billing period and the days the tenant lived there during it. Divide the bill by the period days to get a daily cost, multiply by the tenant’s days, then apply their split share if the bill is shared. A $120 bill over 30 days is $4.00 a day; 12 days is $48.00.
Do you count the move-out day?
This calculator counts both the first day of the period and the move-out day as occupied days. Some leases count the move-out day as the landlord’s. Use whatever your lease says and adjust the date to match.
What is the split share for?
If one master bill covers several units, the departing tenant only pays their part. Enter their RUBS percentage, such as 30%, and the calculator applies it after prorating by days. Use the RUBS calculator to find that percentage.
Is this legal advice?
No. It does the arithmetic only. Rules on billing tenants for utilities and on deposit deductions vary by state and city, and your lease must allow it. Check local law before you bill.