How it works
How this tool works.
When a tenant moves in or out partway through a month, they owe only part of the rent — but there’s more than one accepted way to split it, and the two methods rarely land on the same number.
This calculator shows both: the actual-days method (dividing by the real number of days in that month) and the 30-day “banker’s” method (always dividing by 30). Enter the full rent and the dates and compare — then let your lease decide which one governs.
Enter the full monthly rent, pick how many days are in the month (28, 29, 30, or 31), and set how many days the tenant occupies.
Actual-days method: rent × (days occupied ÷ days in that month).
30-day (banker’s) method: rent × (days occupied ÷ 30) — a fixed 30-day month regardless of the calendar.
The tool shows both results and the gap between them; which one applies is usually written in the lease (and sometimes shaped by local rules).
Make the result useful
Rent-proration decisions
Monthly rent is the contractual recurring rent for the period.
Move-in or move-out dates define the partial occupancy period.
Proration method is the lease or jurisdiction-required calendar-day or fixed-day approach.
Days in month matters only for calendar-day methods.
The assumptions that move this result
Monthly rent
Stated recurring lease rent.
Dates
First and last chargeable days.
Method
Calendar-day or fixed-day formula used.
Days
Chargeable days derived from selected dates.
prorated rent = periodic rent converted under the selected method × chargeable days
Use the output as a documented scenario result, not a guarantee.
Read the number in context
Worked scenario
Scenario: $1,800 over a 30-day method is $60 per day; 10 days is $600.
Edge case
Edge case: a 31-day calendar month produces a different daily amount than a 30-day method.
The tool does not determine the legally required method or create a notice.
Before you act
• Confirm the lease proration clause.
• Use one method consistently.
• Document the dates and method on the ledger.
Worked formula
prorated rent = periodic rent converted under the selected method × chargeable days
Is this a forecast?
No. It calculates the assumptions you enter.
Can it replace professional review?
No. Use current records and qualified advice.
What should I save?
Keep the assumptions and source records used for the decision.