Prorated Rent: 30 Days vs 31 Days Explained
Should you divide monthly rent by 30 or 31 days? Compare the four main proration methods and understand which calculation is fairest for your situation.
$750.00
$1500.00 ÷ 30 × 15 days
Daily rate: $50.00/day
$725.81
$1500.00 ÷ 31 × 15 days
Daily rate: $48.39/day
$739.64
$1500.00 ÷ 30.42 × 15 days
Daily rate: $49.31/day
$739.73
($1500.00 × 12) ÷ 365 × 15 days
Daily rate: $49.32/day
30 vs 31 Day Difference
For your $1,500 rent with 15 days: the difference between 30 and 31 day methods is $24.19. This can add up over multiple partial months!
Understanding the Four Proration Methods
When you need to calculate prorated rent, you'll encounter different methods for determining your daily rate. The method you use can mean a difference of $20-50+ per month. Here's how each works:
How it works: Assumes every month has exactly 30 days, regardless of the actual calendar.
Common in: Commercial leases, standardized property management software
How it works: Uses the real number of days in the specific month (28, 29, 30, or 31).
Common in: Residential leases, court-ordered calculations, California law
How it works: Divides the year by 12 to get an average month length of 30.42 days.
Common in: Some corporate landlords, mathematical precision contexts
How it works: Converts to annual rent, then divides by 365 days for a true daily rate.
Common in: Some European markets, accounting precision contexts
Which Method Should You Use?
For Tenants: Use Actual Days
The actual days method is fairest and is the default in most states. If your landlord insists on 30 days, request actual days be written into your lease.
For Landlords: Check Your Lease
Whatever method your lease specifies is legally binding. If silent, the actual days method is typically applied. Be consistent across all tenants.
The February Factor
February creates the most dramatic difference between methods because it only has 28 days (29 in leap years):
Example: $1,500 rent, 14 days in February
- 30-day method: $1,500 ÷ 30 × 14 = $700.00
- 28-day actual: $1,500 ÷ 28 × 14 = $750.00
- Difference: $50 more with actual days method
In February, actual days favors the landlord. In 31-day months, it favors the tenant.