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Partial Month Rent Calculator
When a tenant moves in or out mid-month, the rent has to be prorated. Three standard methods produce three different answers: 'actual days in month' (fairest), '30-day month' (simplest), and 'banker's month' (365/12 = 30.4167 days — common in property management software). This calculator runs all three so you can match what the lease specifies or the one the tenant expects.
28/29 (Feb), 30, or 31
Last occupied day; equal to days in month for full end
Prorated rent (actual days)
$1,219
Prorated rent (30-day method)
$1,260
Prorated rent (banker's month)
$1,243
Days occupied
18
Per-day rate (actual days)
$67.74
Per-day rate (30-day)
$70.00
Per-day rate (banker's)
$69.04
How the math works
Three methods, three slightly different answers. On $2,100/month with 14 days occupied in a 31-day month, actual-days gives $948.39, 30-day gives $980.00, and banker's gives $966.60. The 30-day method is simplest but overcharges in 31-day months and undercharges in 28/29-day months. Actual-days is the fairest and is what most courts prefer if the lease is silent.
The key rule: match what the lease specifies. If the lease says '1/30th per day,' you use 30-day. If it's silent, actual-days is the default in most landlord-tenant codes. Don't default to whatever the PMS spits out — read the lease.
How to Use
- Enter the full monthly rent.
- Enter the month and year (to calculate actual days in the month).
- Enter the move-in and move-out days (inclusive).
- See all three proration methods side by side and the per-day rate for each.
Frequently Asked Questions
Which proration method is standard?
Landlord-tenant leases most commonly use 'actual days in month' — rent ÷ days in that specific month × days occupied. Commercial and REIT accounting often use the 30-day method regardless of calendar. Banker's month (365/12) is a compromise used by many property management software platforms. Always follow what the lease says verbatim.
Should I charge day of move-in?
Most leases say yes — the move-in day counts as occupied since the tenant has possession and keys. Move-out day is usually charged too if the tenant has keys at any point that day. Exception: some leases define 'day' as 11:59pm to 11:59pm, which would zero out a morning move-out.
What about partial pet rent, utilities, parking?
Prorate everything tied to time-of-month access at the same method. If pet rent is $50/month and the tenant moved in on day 15, pet rent prorate is $50 × (16/30) = $26.67 at the 30-day method. Don't prorate one-time fees like move-in admin.
Is it fair to round up?
Rounding to the nearest dollar each direction is standard. Systematic rounding up is legally risky and often violates state consumer-protection statutes if it adds up. Use the math result and round to the cent; if you want cash simpler, round to the nearest dollar in the tenant's favor.
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