Late Rent Interest Calculator - Calculator Academy

Calculate late rent interest, days late, annual interest rate, rent amount, or interest due when you enter any 3 of 4 values here.

Late Rent Interest Formula

The late rent interest calculation uses simple daily interest based on a 365-day year.

I = R * (r/100)/365 * d

I = interest due
R = rent amount
r = annual interest rate as a percent
d = number of days late

To solve for a missing value, the same formula is rearranged:

d = I / (R * (r/100)/365)

r = (I / (R * d)) * 365 * 100

R = I / ((r/100)/365 * d)

This assumes simple interest, no compounding, and 365 days per year. It does not include late fees, court costs, grace periods, or local legal limits. Check the lease and applicable landlord-tenant law before charging interest.

Useful Late Rent Interest Tables

Use this table to estimate how quickly interest adds up for each $1,000 of unpaid rent.

Annual interest rate	Interest per day per $1,000	Interest for 30 days per $1,000
3%	$0.08	$2.47
5%	$0.14	$4.11
10%	$0.27	$8.22
12%	$0.33	$9.86
18%	$0.49	$14.79

These inputs control the result.

Input	What to enter
Rent amount	The unpaid rent balance, not including separate late fees.
Annual interest rate	The yearly rate allowed by the lease or law.
Days late	The number of days after the due date or after any grace period.
Interest due	The dollar amount of interest owed for the late period.

Late Rent Interest Example

If rent is $1,500, the annual interest rate is 10%, and payment is 14 days late, the interest is:

$1,500 × 0.10 ÷ 365 × 14 = $5.75

The result is only the interest amount. Add any valid late fee separately if the lease and local rules allow it.