How to Prorate the First Month of Rent (and Get It Right)

Published 2026-08-21

A tenant moves in on the 15th. What do they owe for that month? It sounds like arithmetic and it is really a lease-drafting question, because there are three defensible answers and they differ by real money.

The three methods

Take a $1,600 monthly rent and a move-in on 15 July, a 31-day month. The tenant occupies 17 days.

• Actual days in that calendar month. Divide rent by the days in that specific month, multiply by days occupied. 1600 divided by 31 is $51.61 per day; times 17 days is $877.42.
• Flat 30-day month. Divide by 30 regardless of the real month. 1600 divided by 30 is $53.33 per day; times 17 is $906.67.
• Annualized, 365 days. Multiply rent by 12, divide by 365. That is $52.60 per day; times 17 is $894.25.

Same rent, same move-in date, a $29.25 spread. None of them is wrong. What is wrong is not saying which one you use.

Which to choose

The actual-days method is the one to default to. It is the easiest to explain to a tenant — you pay for the nights you have the place, at this month's daily rate — and it is the one a court or housing agency is least likely to find surprising. Its only quirk is that the daily rate moves slightly by month, which bothers spreadsheets more than it bothers people.

The flat 30-day method is popular because it is tidy, and it systematically favours the landlord in 31-day months and the tenant in February. That asymmetry is precisely why some jurisdictions and many tenant advocates dislike it. The annualized method is the most even-handed over a year but the hardest to explain on the spot.

Whichever you pick, name it in the lease. One sentence — "partial months are prorated at the monthly rent divided by the number of days in that calendar month, multiplied by the days of occupancy" — removes the entire category of argument.

The cases people get wrong

February. Under the actual-days method a February day costs more than a July day. That is not a bug; the tenant is paying the same monthly rent for a shorter month either way. Under a flat 30-day method, a full February would technically compute to less than the rent, which is why flat-30 users have to special-case whole months.

Move-out, not just move-in. If your lease ends mid-month, the last month prorates on the same basis. Applying proration only to the first month and charging a full final month is a common and indefensible inconsistency.

A lease that starts and ends in the same month. This is the case that breaks naive calculators. If a tenancy runs 10 June to 20 June, the answer is the 11 days actually occupied — not the 21 days from the 10th to month-end, and not the 20 days from month-start to the 20th. Any proration routine that handles first-month and last-month as two separate rules will compute one of those wrong answers unless it accounts for both bounds at once.

Everything that is part of monthly rent. If pet rent, parking or a monthly utility charge is part of what is owed each month, it prorates too. Pick one basis and apply it to the whole monthly total, rather than prorating base rent and charging a full month of parking.

What does not prorate

The security deposit is not rent and is never prorated — it is a fixed sum held against the tenancy, not a monthly charge. Neither are one-time fees like an application fee or a key deposit. And be careful with a "first and last month's rent" arrangement: if the first month is partial, be explicit about whether the last-month payment is a full month or matches the prorated amount, because tenants and landlords reliably assume opposite answers.

A practical sequencing tip

Many landlords collect the prorated amount at move-in and then start the full-rent cycle on the 1st of the following month. That is cleaner than shifting the due date to the 15th forever, and it means every subsequent month is a normal month. If instead you keep the due date on the move-in day, say so in the lease and be consistent about late fees and grace periods relative to that day.

How this works in PropertyFolio

PropertyFolio prorates on the actual-days basis, using the real number of days in that specific calendar month, and it handles the first month, the last month, and the case where a tenancy begins and ends inside one month as a single calculation rather than as two competing rules. Prorated months are flagged as prorated on the rent schedule so you can see at a glance why one month is different from the eleven around it, and the same figure flows into what the tenant is asked to pay and into your budget and year-end totals.

Set up a lease with prorated rent in PropertyFolio — free to start.