Start with the number of days in the month the tenant will move in.
Take the amount of monthly rent and divide by the number of days in the month the tenant will move in to get the amount owed per day. (Tenant moves in on Aug. 20th. There are 31 days in Aug.)
Find the number of billable days in month by subtracting the number of days in the month plus one. For Example, if the move in day is August 5th , subtract 5 from 31 plus 1 is 27 billable days.
Multiply the amount per day by the number of billable days in the month to find your prorated amount.
Example: Move in August 20th with a rent due date of September 1th.
$1000.00 / 31 = $32.26 x 12 days = $387.10