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Prorated Rent Calculator

Range: 0 – 1,000,000

Range: 1 – 31

Range: 0 – 31

Result

464.52

Prorated rent

Daily rent
38.71
Remaining rent for the month
735.48
Same days on a 30-day month
480.00

A prorated rent calculator for the partial month at the start or the end of a tenancy: tell it the monthly rent, how many days you are being charged for, and how many days are in the month, and it returns the rent for those days along with the daily rate it was built from. The number that decides the answer is not one of yours, though — it is the convention, and there are three in common use: divide by the days actually in that month, divide by 30 whatever the month, or divide by the days in a nominal month your lease names. This page computes the first and shows the third next to it, because the same twelve days in a 31-day month are 464.52 under one and 480.00 under the other, and which of those is the rent you owe is a question about your lease rather than about arithmetic. Nothing here reads a calendar: you supply the days in the month, so the answer follows the convention you were given rather than one this page assumed.

The same days charged out of a 1,000.00 month, under three month lengths

Days occupied28-day month30-day month31-day month
5178.57166.67161.29
10357.14333.33322.58
15535.71500483.87
20714.29666.67645.16
25892.86833.33806.45

The rent is held at 1,000.00 so that one column can be compared with another: only the number of days in the month changes across the row, and only the days occupied change down the column. Read it across the 15-day row to see the spread the convention alone creates — 535.71 in February and 483.87 in a 31-day month, a difference of 51.84 on the same fifteen days — and down the 31-day column to see that the same day of the month costs less in a longer month. A 30-day month is the middle column, and it is the only one where a full month of days costs exactly the monthly rent.

Formula

Daily rent = monthly rent ÷ days in the month; prorated rent = monthly rent × days occupied ÷ days in the month. The 30-day variant replaces the days in the month with 30: prorated rent = monthly rent × days occupied ÷ 30.

monthly rent
The full month's rent from the lease, not the amount that would be due for a shorter month
days in month
The denominator you are being charged on: 31 for a 31-day month, 30 for the 30-day convention, 28 for February — this is the convention, entered as a number
days occupied
The days being charged for, counted the way the lease counts them rather than the way you moved in
daily rent
Monthly rent divided by the days in the month, shown for reference and not used to derive the main result
prorated rent
The answer: the month's rent scaled by the share of the month being charged
30-day rent
The same days computed the other way, on the 30-day convention, printed beside the first answer so the two can be compared

Use it whenever a tenancy starts or ends inside a month and the lease says the rent is prorated, or when you are checking a figure a landlord has already worked out. Put the lease's own convention in the days-in-month box — if it says a month means 30 days, enter 30 even in a 31-day month, because that is the instruction you are following. Check the result against the remaining-rent row as well: the two together should add back to the full month, and if they do not, the convention or the day count is the place to look rather than the arithmetic.

Worked examples

  1. 12 days of a 31-day month at 1,200.00

    1. Daily rent: 1,200.00 ÷ 31 = 38.7096…, shown as 38.71
    2. Prorated rent: 1,200.00 × 12 ÷ 31 = 464.5161…, rounded to 464.52
    3. The rest of the month: 1,200.00 − 464.52 = 735.48, which adds back to the full month exactly
    4. On the 30-day convention the same 12 days cost 1,200.00 × 12 ÷ 30 = 480.00, which is 15.48 more

    The default case, and the one that shows why the convention matters: dividing by 31 rather than 30 makes each day cheaper but leaves a 31st day to be paid for, and the difference here is 15.48 on a 1,200.00 rent.

  2. 10 days of a 30-day month at 1,200.00, where both conventions agree

    1. Daily rent: 1,200.00 ÷ 30 = 40.00, an exact figure with no rounding
    2. Prorated rent: 1,200.00 × 10 ÷ 30 = 400.00
    3. The rest of the month: 1,200.00 − 400.00 = 800.00, which is twice the part being charged for
    4. The 30-day convention gives the same 400.00, because the month being divided is already a 30-day one

    This is the only month in which the two conventions are the same calculation, and the only one where the daily rate comes out exact. A daily rate of 40.00 times 10 days equals the prorated figure to the cent; in months of 31 days it does not, which the last example shows.

  3. 15 days of a 28-day February at 1,500.00

    1. Daily rent: 1,500.00 ÷ 28 = 53.5714…, shown as 53.57
    2. Prorated rent: 1,500.00 × 15 ÷ 28 = 803.5714…, rounded to 803.57
    3. The rest of the month: 1,500.00 − 803.57 = 696.43, which adds back to the month exactly
    4. On the 30-day convention the same 15 days cost 750.00, which is 53.57 less — the short month makes each day dearer and the 30-day rule cheaper

    February is where the two conventions pull hardest in opposite directions: dividing by 28 makes one day of February the most expensive day of the year, while the flat 30-day rule charges the least for it. The gap here is 53.57 on a 1,500.00 rent.

  4. A full 31-day month: all 31 days of 1,200.00

    1. Prorated rent: 1,200.00 × 31 ÷ 31 = 1,200.00, the whole month
    2. The rest of the month: 1,200.00 − 1,200.00 = 0
    3. Daily rent still displays as 38.71, because it is the month's rent over the month's days regardless of how many days are being charged
    4. The 30-day convention would charge 1,240.00 for the same 31 days — 40.00 more than the month actually costs

    Useful as a check rather than as a case: a full month must come out at exactly the monthly rent, and the 30-day column showing more than the month's rent is the clearest sign of what that convention does to a long month.

  5. 29 days of a 31-day month at 1,200.00, where the daily rate and the prorated figure disagree by a cent

    1. Prorated rent: 1,200.00 × 29 ÷ 31 = 1,122.5806…, rounded to 1,122.58
    2. The rest of the month: 1,200.00 − 1,122.58 = 77.42
    3. Daily rent displayed: 38.71, which multiplied by 29 gives 1,122.59 — one cent more than the prorated figure
    4. The 30-day convention charges 1,160.00 for the same 29 days

    The one-cent witness. Multiplying the displayed daily rate by the days is not the same as prorating the month, because the daily rate is itself a rounded number and the rounding is then multiplied by 29. The prorated figure is computed from the month's rent directly and is the one to use; the daily rate is shown for reference.

Limitations

This page does arithmetic on the convention you give it, and the convention is not its to choose. Whether a partial month is divided by the days in that month, by 30, or by some other number the lease names is settled by the lease, and where the lease is silent it is settled by local practice or by whatever the landlord and tenant agree; no federal rule decides it and most state residential tenancy statutes do not either. The two sources cited below are cited for that point, not for a day-count rule of their own — so treat the result as a figure to check against your lease, not as a legal entitlement. Three further things are outside the page. It prorates rent and rent only: utilities, a parking space, a pet fee, a cleaning charge and a security deposit are usually handled by their own clauses, and a deposit is normally refundable rather than earned by the day. It does not count days in residence against days billed — a lease may charge from the first of the month or from the day the keys were handed over, and a month-to-month tenancy with a notice period has its own rules about which day the tenancy ends. And it takes the days in the month from you rather than from a calendar, so a February in a leap year is entered as 29 days if that is the convention you are following; the page cannot know which February you mean because it never sees a date.

Frequently asked questions

How is prorated rent calculated?
Divide the monthly rent by the number of days in the month to get a daily rate, then multiply by the days being charged for. On a 1,200.00 rent, a 31-day month gives 38.71 a day, so 12 days cost 464.52. The division is the whole calculation, and the only judgement in it is which number goes on the bottom.
Should a partial month rent be divided by 30 or by the days in the month?
Whichever your lease says, and if it says nothing, whichever the two of you agree. Dividing by the days in the month is the more literal reading — you pay for the days that exist — while the 30-day convention treats every month as the same length, which is simpler and slightly cheaper in a 31-day month. The two differ by more than a rounding error: 12 days at a 1,200.00 rent is 464.52 one way and 480.00 the other, and 15 days of a 28-day February at a 1,500.00 rent is 803.57 against 750.00.
How many days do I count when I move in mid-month?
Count the days the lease charges for, which is usually from the day the tenancy starts up to but not including the first of the following month. Whether the move-in day itself is charged is one of the small things leases differ on, and it is worth reading the clause rather than assuming: one extra day on a 1,200.00 rent in a 31-day month is 38.71. If you are charged from the first of the month and moved in later, the days you did not occupy are still billed unless the lease says otherwise.
Why does multiplying the daily rent rate by the days not match the prorated figure?
Because the daily rate displayed is a rounded number, and multiplying a rounded number multiplies its error. On the 29-day example above, 38.71 × 29 = 1,122.59 while the prorated rent is 1,122.58 — one cent apart. The main result is computed from the month's rent directly and does not pass through a rounded intermediate, so it is the figure to use; the daily rate is there to be read, not to be multiplied.
What about the last month, when a tenancy ends partway through?
The same calculation, with the days counted from the first of that month to the day the tenancy ends. The remaining-rent row is the useful one here: it is the full month's rent minus what is being charged, and the two figures should add back to the month exactly, which is what makes it a check on the day count as well as on the arithmetic. If they do not add up, a day has been counted twice or left out.
Is a 30-day month the same as a banker's month?
They are close cousins and worth keeping apart. The 30-day convention for rent says a month of rent means 30 days of rent, whatever the calendar says, which makes 31-day months slightly cheaper for a partial tenancy and February dearer. A banker's month is the same idea used for interest, where a year is 360 days and a month 30, so that half a month is always 15 days. Both exist to make the arithmetic uniform, and both put a number in the denominator that the calendar does not have.

References

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