How to prorate rent: the three common methods
Actual days, flat 30-day month and yearly daily rate compared, with worked numbers and how move-in versus move-out timing changes the total.
Why partial months need proration
Leases are quoted per month, but tenants rarely move in on the first and out on the last day. Proration converts the monthly rent into a daily rate and charges only for the days the unit is actually held. The landlord collects a fair amount and the tenant avoids paying for days they did not live there. The only real decision is which daily rate to use, because the month length you divide by changes the answer.
Actual days versus a flat 30 days
The actual-days method divides the rent by the true number of days in that month, so a 31-day month has a lower daily rate than a 28-day February for the same rent. The flat 30-day method ignores the calendar and always divides by 30, which keeps the daily rate identical every month and is easy to reconcile. In a 31-day month the flat method charges slightly less per day, while in February it charges more, so the two can disagree by a few dollars on the same move-in date.
The yearly daily rate
Some leases spread the annual rent evenly by taking the monthly rent times 12 and dividing by 365. This produces one constant daily rate for the whole year, which many property managers prefer because a partial January costs the same per day as a partial July. For a $1,500 rent that daily rate is about $49.32, close to but not the same as the $50.00 you get from a 30-day month. Over a full month the small daily differences roughly cancel out.
Move-in and move-out timing
For a move-in you usually count from the move-in date through the last day of the month, so moving in on the 21st of a 30-day month is 10 occupied days. For a move-out you count from the first of the month through the final day of tenancy. Always confirm with your lease whether the move date itself counts as an occupied day, because including or excluding it shifts the total by one day of rent. Enter that agreed day count into the tool to see the exact figure.