Prorated Rent Calculator: All Three Methods, Side by Side

What is prorated rent?

Prorated rent is the partial rent owed when a tenant occupies a home for only part of a month — almost always the first month (a mid-month move-in) or the last month (a mid-month move-out). Instead of charging a full month for a home you only lived in for eleven days, the rent is divided down to a daily rate and multiplied by the days you actually held the place. Simple in concept; the wrinkle is that there are three legitimate ways to do the division, and they don’t all land on the same number.

How do you calculate prorated rent?

Every method follows the same two steps: find a daily rate, then multiply by the days occupied. The daily rate is monthly rent divided by some number of days — and that divisor is the only thing the three methods disagree on. Days occupied is counted inclusively: for a move-in, from the move-in date through the last day of that month; for a move-out, from the 1st through the move-out date. The move day itself counts. A $1,300 rent with a move-in on the 20th of a 30-day month means 11 days occupied (the 20th through the 30th), and the bill is 11 × the daily rate.

The three proration methods — and which to use

Actual days (the default). Divide rent by the actual number of days in that specific month — 28, 29, 30, or 31. February’s daily rate is higher than July’s because the month is shorter. The defining virtue: a full month always comes to exactly one month’s rent, and the numbers never drift. This is the most common method and the easiest to defend in a disagreement.

Banker’s 30 (the flat-30 method). Divide rent by 30 every month, regardless of the calendar, treating a 31st day as the 30th. It’s the simplest to do in your head, which is why it’s widespread — but it isn’t self-consistent: a full 31-day month billed at rent ÷ 30 × 31 would exceed a month’s rent (so the 31st is capped), and a full February billed at rent ÷ 30 × 28 comes to less than a full month. Fine for a quick estimate; watch the month edges.

Annual / 365. Compute one steady daily rate for the whole year — rent × 12 ÷ 365 — and multiply by the actual days occupied. Every day of the year costs the same, which some landlords prefer for consistency across a portfolio. The trade-off is that a full calendar month rarely equals exactly one month’s rent, since months aren’t all 365 ÷ 12 days long.

Which should you use? Whichever your lease specifies — that’s the real answer. When the lease is silent, actual-days is the sensible default because it’s exact and self-consistent. The calculator above shows all three at once precisely so you never have to guess which one a single-number tool chose; you match the method to your agreement.

Move-in vs. move-out proration

The two cases are mirror images. A move-in partial month runs from the move-in date to the end of the month — you’re paying for the tail of the month you arrived in. A move-out partial month runs from the 1st to the move-out date — you’re paying for the front of the month you leave. Same daily rate under a given method; only the day-count direction flips. The toggle above switches between them, and the plain-English line under the result spells out exactly which days you’re being charged for so there’s no ambiguity.

The tricky months: February, leap years, and 31-day months

This is where methods visibly diverge and where cheap calculators get it wrong. February has 28 days (29 in a leap year), so under actual-days its daily rate is the year’s highest — a few days in February cost more per day than in any other month. Under banker’s 30, February is billed as if it had 30 days, so a full February comes to less than a month’s rent. Leap years add a 29th day to February; a full leap-February under actual-days still equals exactly one month’s rent (rent ÷ 29 × 29), while a fixed-rate method won’t. And 31-day months expose the banker’s-30 seam directly: the 31st is treated as the 30th, so a move-in on the 31st bills a single day either way, but a move-in early in a 31-day month bills slightly less under flat-30 than under actual-days. The calculator handles all of it — real calendar lengths, leap years, and the day-31 cap — so the number you see is the number that reconciles.

A note on what’s “correct”

There isn’t a single universally-mandated method — proration is set by your lease and local practice, and this tool doesn’t make legal determinations or offer legal advice. What it does is compute each method exactly and show them together, so you can check a landlord’s figure, propose a fair one, or simply understand why two calculators disagree. Match the method to your agreement, get it in writing, and the math above will reconcile to the penny.

Put this calculator on your website

Property managers, leasing agents, landlord blogs, tenant-resource sites — if your audience deals with move-in math, embed this calculator free with one line of HTML. It sizes itself to any page, works on mobile, and shows all three methods so it answers the question instead of raising a new one.

<script src="https://onemoredoor.com/omd-embed.js" data-calc="prorated-rent"></script>