Prorated Rent Calculator

What prorated rent is

Rent is billed by the month, but people move in and out on the days that suit them. Prorated rent is the part of a month's rent that matches the days someone holds the keys. Move in on the 15th and you owe for the back half of the month; move out on the 12th and you owe for the first twelve days, not the whole month.

Two numbers decide the result: the daily rate and the number of billable days. The daily rate is where landlords differ, because nothing forces them to divide by the same denominator. The day count is where tenants and landlords argue, because it depends on whether the move-in day itself counts, and whether the keys change hands on the first or the last day named in the lease.

The math matters at both ends of a lease. A first month that is short by a hundred dollars is a surprise at signing, and a last month that is short by the same amount turns into a deduction from the deposit that takes weeks to argue about. Getting both numbers in writing before the money moves avoids the argument entirely.

Three ways to set the daily rate

The first method divides the monthly rent by the actual number of days in that calendar month. It is the most calendar accurate option, and it produces a different daily rate in February than in August. The second method divides by a flat 30 days no matter which month it is, which is easy to explain and easy to compute by hand. The third method multiplies the monthly rent by 12 and divides by 365, which gives one daily rate that holds all year.

None of the three is wrong on its own. What matters is that the lease names one and applies it every time, because switching methods mid lease is how the totals stop matching the ledger. The choice also has a direction: the flat 30 day method charges more per day than actual days in a 31 day month and less in February.

Month length changes the daily rate under the actual days method, which is why two identical moves can cost different amounts depending on the calendar.

Run the same table for February and the order flips. A 28 day month makes the actual days rate 64.29, higher than either fixed method, so a tenant who moves in on February 20 with 9 days left pays 1,800 x 9 / 28 = 578.57 under the actual days method and 1,800 x 9 / 30 = 540.00 under the flat 30 day method.

Worked example: moving in on October 15 at $1,800

October has 31 days. The keys are handed over on the 15th, so the billable days are 31 - 15 + 1 = 17, counting the 15th itself. Under the actual days method the bill is 1,800 x 17 / 31 = 987.10, which works out to 58.06 per day.

Under the flat 30 day method the bill is 1,800 x 17 / 30 = 1,020.00, or 60.00 per day. Under the 365 day method the yearly rent is 1,800 x 12 = 21,600, so the bill is 21,600 x 17 / 365 = 1,006.03, a daily rate of 59.18.

The spread between the cheapest and the most expensive method is 1,020.00 - 987.10 = 32.90. That is small next to a month's rent, but it is worth knowing which column you are in before you sign, because the same clause governs the last month too.

Worked example: moving out on November 12

Leaving is the mirror image. November has 30 days, the unit is occupied from the 1st through the 12th, and the billable days are 12, because the month starts on day one. Under the actual days method the bill is 1,800 x 12 / 30 = 720.00, which is 60.00 per day.

The 365 day method gives 1,800 x 12 x 12 / 365 = 710.14, which is 9.86 less. The flat 30 day method lands on the same 720.00 as actual days, since November already has 30 days. When the month length and the fixed denominator agree, two of the three methods collapse into one answer.

Watch the handover date here. A lease that runs through November 30 but allows an early return of the keys on the 12th still owes the full month unless the lease says otherwise, and a landlord who agrees to release the unit early should put that in writing. Prorating a last month is a concession in most leases, not a right.

Counting the days, including the day you move

The count starts on the day the unit becomes yours and ends on the last day of the month, both included. That is why October 15 produces 17 days rather than 16: the 15th, 16th, 17th and so on through the 31st. A move on the first of the month gives the full count, and a move on the last day gives one day.

The formula is days in the month minus the move-in day plus one. For a move-out, the count is the move-out day number, because the month starts at day one. The plus one looks trivial and causes most of the disputes, since one day at 60 dollars is a real amount of money and the two sides often count differently.

Some leases tie the billable day to midnight rather than to the keys. If the lease starts on the 15th but the office hands over keys on the 14th after 4 pm, the written date decides, not the key handover. Read the start date in the lease and use that number, then ask the office to confirm the prorated figure in writing before paying it.

What the lease and local rules decide

No federal rule sets how a partial month of rent is calculated. The lease is the first authority, and state landlord tenant law is the second. Some states spell out how rent is apportioned when a tenancy ends mid month, and some cities with rent boards add their own rules, so the answer can change at a city line.

The practical steps are the same everywhere. Read the rent section of the lease for a prorating clause, note whether it names a method, and compare the number on the invoice against your own arithmetic. If the two disagree, ask for the daily rate in writing rather than asking for a new total, since the daily rate is the number that has to be defended.

For questions about tenant rights in general, USAGov's tenant rights page explains how to raise a complaint with a landlord and which local agency handles disputes. Rental assistance programs, which often have their own rules about partial months, are listed through HUD's rental assistance page. Neither source sets a formula, and that is the point: the lease and local law do.

Deposit, last month and utilities

Security deposits are usually not prorated. A deposit is typically a fixed amount, often one month's rent, and it is collected in full at signing even when the first month is partial. An $1,800 apartment with a $1,800 deposit and a move-in on October 15 can therefore cost 987.10 plus 1,800.00, or $2,787.10, before the first utility bill arrives.

Some landlords collect first month, last month and deposit together. In that case the last month is usually charged at the full rate, because the lease end date may be a full month away, and any proration is settled when the tenant leaves. Get the treatment in writing, since three months of rent up front changes the cash needed to move.

Utilities prorate on the same idea but with different denominators. Water, gas and electricity bills cover a billing period that rarely matches the calendar, so the split usually comes from meter readings on the move dates. The prorated utility split calculator handles that case, and the divisor there is the days in the billing period rather than the days in the month.

Where the math goes wrong

Three errors account for most bad prorated bills. The first is dividing by 30 out of habit while the lease says actual days, which overcharges in a 31 day month by about 2 dollars a day and undercharges in February by more. The second is dropping the plus one, which costs a tenant one day of rent and shows up as a total that is exactly one daily rate low.

The third is using the move-out month's length for a move-in that happened in a different month. A lease that starts on the 28th of January and bills in February needs January's 31 days for the first partial month, not February's 28. The month that gets divided is the month being billed, and the days counted belong to that same month.

Rounding is the last wrinkle. Two decimal places on the daily rate, then multiply, gives a total that can differ by a cent or two from dividing the total rent by the days. State the rounding rule in the lease, or at least use the same order of operations every month, so the ledger stays internally consistent.