Micro utility
Prorate rent, salary, subscriptions, vacation allowance, or any custom allocation with live math, clear warnings, and a copy-ready breakdown.
Pick a preset to swap the labels and defaults for the scenario you are working on.
Enter the full rent for the month before any discounts or credits.
Use the total number of calendar days in the billing month.
Count the days the tenant is responsible for in that month.
Enter the total directly
Type the total number of days if you already know the count.
Pick occupied days
Toggle the exact days you want to count. The total updates automatically.
0 selected out of 30
Worked example
Pro rata math is usually easiest to trust when it is tied to one clear scenario. Rent is the most common version people need to sanity-check quickly.
A tenant moves in partway through a 30-day month, so the first payment should only cover the days actually occupied.
Example assumptions
36.7% of the full month
Worked example math
This is the heart of the calculator: take one full amount, apply the real share of the period used, and make the partial payment obvious instead of negotiated by guesswork.
How it works
The calculator uses the standard pro rata formula and keeps the current numbers visible so the result stays easy to audit.
General formula
With your numbers
What the warnings mean
Base period must be above zero
The denominator cannot be zero, so the calculator pauses the result and shows a warning instead of producing an invalid number.
Actual units can exceed base units
Over-allocation still calculates, but the result is highlighted so it is clear the actual share has gone beyond 100% of the base period.
Total value
$0.00
Monthly rent
Base period
30 days
Total days in month
Actual portion
0 days
Days occupied
Final result
$0.00
Pro rata amount