What does this calculator do?
Proration converts monthly rent to a daily amount and multiplies it by the number of billable days. Different leases use different denominators, so the same move-in date can produce different charges. The calendar method uses the actual length of that month. The fixed-month method divides by 30. The annualized method divides twelve months of rent by 365 or 366 days.
How to use it
- Check which daily-rate method your lease specifies.
- Count the days you are required to pay, rather than only the days you plan to sleep there.
- Select the calendar length and method, then compare the result with the written invoice.
The math, made clear
Prorated rent = monthly rent ÷ days in month × billable days (calendar method)A worked example
At $1,800 monthly rent, 12 billable days in a 31-day month cost $696.77 using calendar days. The same 12 days cost $720.00 under a 30-day convention. The difference comes from the contract method, not the apartment price.
What to keep in mind
The calculator does not decide whether rent must be prorated. It excludes deposits, utilities, concessions, and fees. Your lease and applicable rules control billing. A 30-day method can exceed a full month of rent for 31 billed days unless the contract caps the charge.
All default values are illustrative. Results are rounded for display; calculations use full precision except where a split must allocate exact cents. Read our methodology for shared definitions and report a calculation issue if a result looks wrong.