Prorated Rent Calculator
Three conventions are in common use and they disagree. All three are here, so you can see which one your lease should be specifying.
The tenancy
September 2026 has 30 days.
Occupied days
19 of 30 days.
Spread between the three methods
$17.35
The lease should say which one governs. When it does not, this is the argument.
| Actual days in the month | $1,266.67Highest$66.67 per day |
|---|---|
| 30-day banker's month | $1,266.67$66.67 per day |
| Annualized (×12 ÷ 365) | $1,249.32Lowest$65.75 per day |
Estimates only. Which method governs is a matter of what the lease says and, where it is silent, of local practice and landlord-tenant law. This is not legal advice.
A trivial calculation with three right answers
Prorating rent is arithmetic a child could do, and it generates a startling number of disputes. Not because anyone gets the multiplication wrong, but because there are three conventions in ordinary use and nothing in most leases says which one governs.
- Actual days. Rent divided by the real length of that specific month. Defensible on first principles: you pay one month’s rent for one month, so a February day costs more than a July day.
- The 30-day banker’s month. Rent ÷ 30, whatever the calendar says. Simple, consistent between months, and it slightly overcharges in 31-day months while undercharging in February.
- Annualized. Rent × 12 ÷ 365. Every day of the year costs exactly the same, which is the fairest treatment across a whole tenancy and the least intuitive to explain at signing.
None is wrong. They just do not agree. On $2,000 rent for 17 days of a 28-day February, the spread runs about $96 — actual days charges the most, annualized the least, and roughly five percent of a month sits between them.
Move the month to July and the ordering inverts: with 31 days the actual-days method becomes the cheapest and the 30-day month the dearest, because a flat 30 divides the rent across fewer days than the month actually has. Anyone who applies one convention in winter and another in summer will, over enough tenancies, be accused of doing it deliberately.
Which is the real point. The money is small; the goodwill is not. A tenant who moves in and immediately feels overcharged by ninety dollars has formed a view of the landlord in week one, and that view is expensive to change. The fix costs nothing: name the method in the lease, apply it to move-in and move-out alike, and show the tenant the arithmetic before they sign rather than after they query it.
Where a lease is silent, local practice and landlord-tenant law decide, and some jurisdictions specify a default. If you own in more than one state it is worth knowing which — and worth not assuming the answer travels.
Methodology
- Actual days: rent ÷ days in that month × days occupied. Leap years are handled.
- Banker’s month: rent ÷ 30 × days occupied.
- Annualized: rent × 12 ÷ 365 × days occupied.
- Days occupied counts both the first and last day inclusive, which is the usual convention — a tenant occupying the 12th through the 28th has 17 days, not 16.
Currency is computed in exact integer cents and rounded once, at display. Excluded: leap-day handling under the annualized method (366-day years still divide by 365, which is the common convention), utilities and fees that may prorate differently from rent, and any local rule that mandates a particular method.
Frequently asked questions
- How do you calculate prorated rent?
- Divide the monthly rent by a number of days to get a daily rate, then multiply by days occupied. The argument is over which number of days: the actual length of that month, a flat 30, or 365 ÷ 12. All three are in ordinary use and they give different answers.
- Which proration method is correct?
- Whichever the lease says. When the lease is silent, local practice and landlord-tenant law fill the gap, and in some jurisdictions there is a default. Actual days is the most defensible on first principles — it charges for the month you actually occupied — but a lease specifying a 30-day month is perfectly enforceable in most places.
- How much difference does the method make?
- More in short months than long ones. On $2,000 rent for 17 days of February the three methods span about $96 — roughly five percent of a month's rent. In a 31-day month the ordering flips and the spread narrows. It is small money, and it is exactly the size of thing that sours a tenancy in its first week.
- Why is a February day more expensive?
- Under the actual-days method the same monthly rent is divided across fewer days, so each one costs more. It is internally consistent — you pay one month's rent for one month regardless — but it means moving in on the 12th of February costs more than the 12th of July for the same 17 days.
- Should rent be prorated on move-out too?
- If the lease allows a mid-month end date, yes, and it should use the same method as the move-in. Using actual days on the way in and a 30-day month on the way out is the kind of inconsistency that ends up in front of a magistrate. Set the last day above to model it.
- What about the first month's rent and deposit?
- Practice varies: some landlords collect a full month up front and prorate the second month, others prorate the first. Both are common and both are fine as long as the lease is explicit. The deposit is a separate matter and is not prorated.
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