Late Fee Calculator

Three common ways late fees are charged

A late fee is the penalty added when an invoice, rent check, or loan installment is not paid by its due date, and contracts almost always use one of three methods. A flat fee adds a fixed dollar amount — $25 or $50 is typical on invoices and leases — no matter how big the balance is or how late the payment runs. A percentage fee charges a share of the overdue balance once; 1.5% per month is a very common invoice term. Daily interest accrues a little every day: the balance times a daily rate times the number of days late, where the daily rate is simply the annual rate divided by 365. This calculator handles all three, then shows the fee, the new total owed, and how heavy the penalty is as a share of the balance. Everything runs in your browser — nothing you type is sent anywhere.

Estimates only — this is not legal or financial advice; late-fee rules, grace periods, and caps vary by state, contract, and industry.

How to use it

1. Enter the overdue amount — the unpaid balance the fee applies to.
2. Pick the method your contract or invoice specifies: flat fee, percentage of balance, or daily interest.
3. Enter the fee or rate. For daily interest, enter the annual rate — the tool converts it to a daily rate for you.
4. For daily interest, add the number of days late.
5. Read the late fee, the new total owed, and the fee as a percentage of the balance. Results update as you type.

FAQ

What is a typical late fee?

Invoices often use 1–1.5% per month or a flat $25–$50. Residential leases commonly charge 5% of rent or a flat amount, though many states cap what a landlord can charge.

How do I turn an annual rate into a daily rate?

Divide by 365. An 18% annual rate is 18 ÷ 365 ≈ 0.0493% per day, so a $1,000 balance accrues about 49 cents a day.

Are late fees legally capped?

Often, yes. Many states cap late fees on rent, loans, and consumer bills, and courts can strike down fees that look like penalties rather than reasonable estimates of damage. Check your state rules and your contract.

Does the fee compound?

This tool uses simple interest — the daily charge is always calculated on the original balance, which matches how most invoice and lease terms are written.