Prorated Rent Calculator

What proration covers.Proration normally applies to a single partial month — most often a tenant’s first month when they move in partway through, or a last month when they move out early. You divide the monthly rent into a daily rate, then multiply by the number of days the tenant actually occupies the unit (counting both the move-in day and the period-end day).

Methods. actual month divides rent by the real number of days in the move-in month (28–31). This is the common default, including in Massachusetts. 30-day month(the banker’s month) divides by 30 regardless of the calendar. 365-day year annualizes the rent (monthly × 12) and divides by 365.

No single legal rule. Proration is a matter of lease terms and common practice, not statute — there is no Massachusetts law dictating a method. When the lease is silent, the actual-days-in-the-month method is the usual default. Always confirm the method written into your lease.