Prorated Rent Calculator
Work out what a tenant owes for a partial month, with the daily rate and the amount due for a mid-month move-in or move-out.
What this calculator does
This prorated rent calculator works out what a tenant owes for a partial month. Enter the monthly rent, the number of days in the month, and the number of days occupied, and it returns the daily rate and the amount due — the arithmetic every mid-month move-in or move-out requires.
The formula is monthly rent divided by days in the month, multiplied by days occupied. Simple as it is, it is worth doing explicitly rather than in your head, because the two figures that matter — the daily rate and the total — should both appear on the invoice and in the lease addendum. Ambiguity about a partial month is a common source of early friction in an otherwise straightforward tenancy.
When to use it
The usual case is a mid-month move-in, where a tenant takes possession on the 12th and the lease then runs on a calendar-month cycle from the 1st. It is equally common when a lease is assigned or a roommate is added partway through a month, and when a tenant on a month-to-month agreement gives notice that expires mid-month.
Landlords also use it when applying a rent increase that takes effect partway through a billing period, prorating the old rate and the new one across their respective days. And it settles small disputes cheaply: when a tenant queries the first invoice, showing the daily rate and the day count usually ends the conversation in one message rather than three.
Understanding the inputs
Monthly rent is the full contract rent, before any concession. If you have granted a free-rent period or a move-in special, apply the concession separately rather than folding it into the rent figure, so both parties can see what was charged and what was discounted.
Days in month determines the method. Use the actual calendar days — 28, 29, 30, or 31 — for the most common approach. Enter 30 to use the flat banker's month regardless of the real calendar, which produces consistent daily rates all year. Days occupied should count the move-in day itself, so a move-in on the 12th of a 31-day month gives 20 days, from the 12th through the 31st inclusive.
How is this calculated?
Prorated Rent = (Monthly Rent / Days in Month) × Days Occupied
A worked example
A tenant moves in on March 12th with rent of $1,800 a month. March has 31 days, and the tenant occupies from the 12th through the 31st — 20 days including the move-in day. The daily rate is $1,800 divided by 31, or $58.06, so prorated rent for March is $1,161.29.
The same tenancy under a flat 30-day month gives a daily rate of $60.00 and a total of $1,200.00 — about $39 more. Under the 365-day method, annual rent of $21,600 divided by 365 gives $59.18 a day and a total of $1,183.56. All three are defensible; none is more correct than the others. What matters is that the lease names one, because the $39 spread is precisely the kind of gap that turns into a dispute.
Limitations and assumptions
The calculator handles the arithmetic, not the agreement. It cannot tell you which method your lease specifies, whether your jurisdiction imposes rules on partial-month rent, or whether the move-in day counts — all of which are matters for the lease and for local law rather than the formula.
It also covers rent alone. Security deposits are never prorated, and one-time move-in or administrative fees are not either, while recurring monthly charges such as pet rent, parking, and flat-rate utilities generally should be, each on the same day count. For a mid-month rent increase, run the calculation twice — once at the old rate for its days and once at the new rate — and show both lines on the invoice.
Common Questions
- Which proration method should I use?
- Three are common: the actual days in that month, a flat 30-day month, and the annualized 365-day method. They give different answers — on $1,800 rent for 20 days, calendar days give $1,161.29, a 30-day month gives $1,200, and the 365-day method gives $1,183.56. Whichever you use, name it in the lease.
- Do I count the move-in day itself?
- Yes. The standard is that the tenant pays for the day they take possession, so moving in on the 12th of a 31-day month means 20 days including the 12th. Getting this wrong by one day is the most frequent source of proration disputes, so state the count explicitly in writing.
- Is prorated rent legally required?
- Not federally, and rarely by state statute — it is a matter of what the lease says. Most landlords offer it as standard practice because charging a full month for a partial one is a bad way to begin a tenancy. Some jurisdictions, including certain rent-controlled cities, do impose rules.
- When is prorated rent usually paid?
- Commonly at move-in alongside the security deposit and first full month, or added to the second month's payment. The second approach is popular because it keeps the tenant's largest outlay at signing simpler. Either works provided the lease states which, along with the amount and the calculation.
- Does proration apply when moving out?
- Only if the lease says so or the landlord agrees. Many leases require a full final month regardless of departure date, especially where a fixed term ends mid-month. Month-to-month agreements requiring thirty days' notice frequently produce a partial final month, and that is where the question usually arises.
- How does proration work in February?
- With the calendar-day method the daily rate changes: $1,800 across 28 days is $64.29 a day, against $58.06 in a 31-day month. A tenant occupying the same number of days pays more in February. That inconsistency is exactly why many landlords prefer the flat 30-day or 365-day method.
- Should the security deposit be prorated too?
- No. A deposit secures the tenancy against damage and unpaid rent and is not a payment for time occupied, so it is charged in full regardless of when the tenant moves in. Many states cap deposits at one or two months' rent and impose strict rules on return timing.
- What about utilities and other charges?
- Prorate anything charged monthly for time occupied — pet rent, parking, and any utility billed as a flat monthly amount. One-time charges such as application fees, administrative fees, and move-in fees are not prorated. Listing each prorated line separately on the first invoice prevents most disputes.
- Can a landlord refuse to prorate?
- Generally yes, unless local law or the lease requires otherwise. In practice it is unusual, and a tenant asked to pay a full month for five days of occupancy has strong grounds to negotiate. Confirm the treatment in writing before signing rather than assuming it will be handled fairly.
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