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Late Fee Effective APR Calculator

Turn a flat late fee into the effective annual interest rate it represents, so you can compare it to borrowing.

Amount owed

Late fee charged

Days late

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How it works

APR = (fee ÷ balance) × (365 ÷ days late) × 100

A flat late fee is a fixed cost for a short delay, so as an annual rate it is enormous. Expressing it as an APR shows just how expensive paying late really is compared with any normal loan.

Worked example

A $40 fee on a $1,000 balance 15 days late is 4% for 15 days — about a 97% APR.

Frequently asked questions

Why is the APR so high?

Because the fee is charged for a short window. Spread over a year, even a small flat fee becomes a very large percentage rate.

Does interest also apply?

Often yes — many accounts add interest on top of the late fee, making the real cost higher than this fee-only figure.

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This is an educational estimate, not financial advice. Confirm exact figures with your lender, employer or a licensed advisor.