Late Payment Fee Calculator
Estimate the total cost of a late payment — the late fee plus any interest that accrues on the overdue amount for the days it is late.
How it works
Late fee = greater of (flat fee, amount × fee%) · Interest = amount × (APR ÷ 365) × days late · Total = amount + late fee + interest
A late charge is usually the greater of a flat fee or a percentage of the missed amount, applied once when the payment is late. On top of that, many balances accrue daily interest on the overdue amount until it is paid, so the longer it stays unpaid the more it costs. This adds both parts to show the full penalty.
Worked example
On a $1,000 payment 15 days late with a fee of "the greater of $25 or 5%", the fee is 5% = $50. At 18% annual interest, 15 days adds $1,000 × (0.18 ÷ 365) × 15 ≈ $7.40, so the total owed becomes about $1,057.40.
Frequently asked questions
How are most late fees calculated?
Contracts commonly charge the greater of a flat dollar amount or a percentage of the overdue payment, capped by any legal maximum. This calculator uses that "greater of" rule; set one of the two to zero if your agreement uses only a flat fee or only a percentage.
Do late fees also add interest?
Often, yes. Credit cards and many loans keep charging their normal interest rate on the unpaid balance every day it is late, separate from the one-time late fee. Set the interest rate to zero if your account does not accrue daily interest.
Can a late payment cost more than the fee?
Yes. Beyond the fee and interest, a payment 30 or more days late can be reported to credit bureaus and damage your score, which can cost far more over time than the fee itself. Paying even the minimum before the 30-day mark usually avoids the credit-report hit.
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Educational estimate only — not financial, tax or lending advice. Confirm exact figures with your lender.