Late Fee Compounding Shocker
Late Fee Calculator — Compounding Cost
What this calculator does
This calculator shows the snowball effect of a missed payment. Late fees, penalty APR, and minimum payment recalculation can make the cost much larger than it first appears.
The math, with a worked example
New balance = missed payment + late fee. Interest = new balance × penalty APR ÷ 12. Minimum payment = new balance × minimum %. Missing a $200 payment with a $40 late fee and 29.99% penalty APR turns the balance into $240, adds $6 in interest the first month, and pushes the minimum payment to $7.20.
Why this matters
One missed payment is never just the late fee. The fee joins the balance, penalty APR starts charging interest on the new total, and the required minimum rises with it. This calculator prices all 3 costs of a single missed month.
Methodology and transparency
New balance = missed payment + late fee; first-month interest = new balance × penalty APR ÷ 12; new minimum = new balance × minimum percentage. The assumption most likely to be wrong: the penalty APR defaults near 30%, but your cardholder agreement sets the real rate and some issuers apply it only after 60 days late. The tool models one month — left unpaid, the interest compounds monthly from there. Everything runs in your browser; no data is sent or stored.
Last reviewed: 2026-08-08
Common questions
How long does a penalty APR last?
Penalty APRs often last 6 months or longer after a missed payment, depending on the card agreement.
Can I get a late fee waived?
Often yes, especially if you usually pay on time. Call the issuer and ask for a courtesy removal.
Does a late payment hurt my credit?
Payments more than 30 days late can be reported and damage your credit score.