What prorated rent is
When you move into (or out of) a rental in the middle of a billing period, you shouldn’t pay for the whole month — only for the days you actually have the place. That partial-month charge is your prorated rent. The math is simple in principle: find a daily rate, then multiply by the days you occupy. The catch is that there is no single legal definition of “daily rate,” and the common conventions give slightly different answers.
The proration formula
Prorated rent = daily rate × days occupied
where the daily rate is monthly rent ÷ days in the month (actual-days method), monthly rent ÷ 30 (flat 30-day method), or monthly rent × 12 ÷ 365 (banker’s-year method).
The three methods — and why they differ
- Actual days in the month. Divides rent by the real number of days that month (28–31). Most common and generally the fairest, since it reflects the true cost of each day.
- Flat 30-day month. Always divides by 30, no matter how long the month is. Simple and written into many leases — but it slightly overcharges in 31-day months and undercharges in February.
- Banker’s year (365 days). Uses an annualized daily rate (rent × 12 ÷ 365) that stays the same every month of the year.
What makes this calculator different
- All three methods, side by side. Most calculators pick one. We show actual-days, flat-30, and banker’s-year together so you can see the spread and match what your lease specifies.
- The dispute, quantified. We surface the exact dollar difference between methods — the few dollars landlords and tenants actually argue about.
- Real month lengths. Pick 28, 29, 30, or 31 days so a February move-in is handled correctly, not approximated.
- Shareable. Copy a link with your exact figures to send to a landlord, tenant, or roommate.
Frequently asked questions
How do you prorate rent?+
Prorating rent means charging only for the days a tenant actually occupies the unit in a partial month. You first find the daily rate, then multiply it by the number of days occupied. The daily rate is the part people disagree on: divide the monthly rent by the actual number of days in that month (the most common method), by a flat 30 days, or by an annualized 365-day year. For example, $1,500 rent with a $50/day rate and 10 days of occupancy comes to $500.
Which proration method is fairest or most common?+
The “actual days in the month” method — monthly rent divided by the real number of days in that month — is the most common and is generally considered the fairest, because it charges the true cost of each day you live there. The flat 30-day method is simpler and appears in many leases, while the banker’s-year (365-day) method gives a consistent daily rate across every month. In a 31-day month these can differ by a few dollars, which is exactly why this calculator shows all three side by side.
Who decides which proration method is used?+
The lease does. A well-written lease states how rent is prorated, and that language controls. If the lease is silent, landlords and tenants should agree in writing before move-in — and absent any agreement, the “actual days” method is the customary default in most places. Some states and cities also have specific rules, so check your local landlord-tenant law.
How do I prorate rent for a mid-month move-out or the last month?+
It works the same as a move-in: count the days you actually occupy the unit in that final month and multiply by the daily rate. If you move out on the 12th of a 30-day month, you owe 12 days of rent. Be careful about whether the move-out day itself counts — leases differ — and confirm the method matches whatever was used when you moved in so both ends are consistent.
Does prorating apply to the security deposit too?+
No. A security deposit is a fixed sum held against damage and unpaid rent, not a charge for time occupied, so it is not prorated — you typically pay it in full regardless of your move-in date. Only the rent itself (and sometimes recurring fees like parking or pet rent) gets prorated for a partial month.
Disclaimer: This calculator is for educational purposes only. Proration conventions and rounding vary by lease, landlord, and local landlord-tenant law. Always check what your lease specifies. It is not legal or financial advice.