Free tool
Prorated rent for a partial month
You arrive on the 12th, you leave on the 20th: here is what you actually owe for that month, based on the calendar days of the month concerned.
Full monthly amount
Month and occupied period
Both ends are included: the 10th to the 31st is 22 days.
Days in the month
30
Days occupied
—
Prorated result
Enter the amounts to see the result.
This is a maths calculator, not legal advice: your lease or local rules may set another convention (a flat 30-day month, for instance). Check what your contract says before applying this result.
Everything is computed in your browser: nothing is stored or sent.
Whole-cent arithmetic with a largest-remainder distribution of the leftovers: the shares are checked against the total by automated tests.
For tracking several expenses over time, with your friends.
The formula
The amount due is the monthly amount times the number of occupied days, divided by the number of days in the selected month. February 2028 has 29 days, April has 30, July has 31: the tool picks the right divisor for you.
A worked example checked by our tests: a monthly rent of 900 in February 2027 (28 days), occupied from the 12th to the 28th inclusive, so 17 days. The share due is 546.43 and the rest of the month is 353.57. The two add back to the exact monthly amount.
Moving in, moving out, being replaced
When moving in, enter from the arrival day to the end of the month. When moving out, from the 1st to the last occupied day. For a mid-month replacement, run the tool twice: the two shares cover the whole month with no gap and no overlap.
If someone occupies the full month, the tool simply returns the monthly amount. That is the quickest way to confirm no date slipped.
Where prorating stops
Prorating settles the rent. It says nothing about the deposit, the insurance or the groceries bought during that same month. Those are tracked separately, expense by expense.
In a flatshare where people come and go, keeping all of that in a spreadsheet gets tedious fast. A shared group where everyone adds their own expenses from their phone removes the end-of-month recount.
Frequently asked questions
Why count calendar days instead of thirtieths?
Because it is a rule that is simple to justify: you pay for the part of the month you actually occupied. Days in a 31-day month cost slightly less than in February, and the yearly total still comes out right.
Does the move-out day count?
Here it does: both ends are included, so the 10th to the 20th is eleven days. If your own convention excludes the last day, enter the day before as the end date.
Should bills be included?
The charges field is there for that. Flat monthly charges prorate exactly like rent. An annual reconciliation is a separate matter, settled once the real readings are known.
Is this calculation legally required?
No. This is a maths calculator, not legal advice. Your lease, your flatshare agreement or local rules may set a different convention, and that convention takes precedence over what you see here.
Editorial review — Written and reviewed by the Pivunio team. The methods described here are the ones the app itself uses, and they are covered by automated tests.