Start with the lease and local rules
The lease usually controls how a partial month is charged, including the divisor and which days count. Some states and cities also regulate rent, notice periods, and move-in or move-out charges. Confirm your lease terms and local requirements before you calculate. If you are unsure, ask the other party in writing or consult a local attorney or your landlord association. This page only shows the arithmetic for three different formulas so you can check a figure.
Formula A: divide by the actual days in the month
daily rate = monthly rent / days in that month prorated rent = daily rate x days occupied
Example: monthly rent $1,500, June (30 days), 10 days occupied. 1,500 / 30 = 50 per day, and 50 x 10 = $500.00. In a 31-day month the same rent gives 1,500 / 31 x 10 = $483.87 (rounded at the end).
Formula B: divide the annual rent by 365
prorated rent = (monthly rent x 12 / 365) x days occupied
Example: monthly rent $1,500, 10 days occupied. 1,500 x 12 = 18,000; 18,000 / 365 x 10 = 493.150... which rounds to $493.15. Keep full precision until the last step and round once, to the cent.
Formula C: fixed 30-day month
prorated rent = monthly rent / 30 x days occupied
For a 30-day month this gives the same $500.00 as Formula A. In a 31-day month it gives 1,500 / 30 x 10 = $500.00 where Formula A gives $483.87. Different formulas give different amounts for the same days, which is why the lease should say which one applies.
Counting days
Whether the move-in and move-out days both count is a lease or local-rule question. The examples above count 10 days for June 21 through June 30, with both ends included.
What to record
- Enter the prorated amount as its own charge in your rent ledger, with a note showing the dates and the formula used.
- Record the start date in your rent roll, and the deposit separately.
- Keep the calculation with the lease.
See the running balance formula to have the ledger total this automatically.
General information, not legal advice.