Calculator
Credit Card Interest Calculator: Project Carrying Costs and Payoff Paths
Model how revolving balances grow based on APR, payment size, and new spending assumptions.
Overview
Credit card interest calculator: see how long a payoff really takes
This calculator simulates month-by-month payoff of a credit-card balance at a given APR with a chosen monthly payment, optionally adding new monthly charges. It is built to expose how slowly minimum payments retire a balance and how quickly a moderate payment increase changes the timeline.
Credit card payoff results
How it works
The simulation, in plain English
Each simulated month: monthly interest = balance × (APR ÷ 12). New balance = balance + interest + new charges − payment. The simulation continues until the balance reaches zero or the payment fails to cover monthly interest (in which case the balance grows forever).
Example
Worked example
A $6,000 balance at 24% APR with a $150 monthly payment and zero new charges retires in roughly 73 months and costs about $4,950 in interest. Increase the payment to $250 and the timeline drops to roughly 32 months with interest near $1,950 — saving about three years and three thousand dollars on the same balance.
Limits
What the calculator cannot model
Real credit-card statements use slightly different daily-balance methods, may reprice on missed payments, and impose minimum payment formulas (often the larger of 1% of balance + interest or a flat dollar minimum). The simulator’s assumption of a constant payment is a simplification. For a debt that you carry close to its limit, real APR repricing risk is the biggest unmodeled factor.
FAQ
Common questions
Should I always pay more than the minimum?
Yes when cash flow allows. Minimum payments are designed to extend revenue to the issuer; even small increases significantly shorten the payoff and reduce total interest.
What if I keep adding new charges?
Use the “new monthly charges” input. If your payment is less than the interest charge plus the new charges, the balance will grow rather than shrink. The simulator will flag this case.
Should I do a balance transfer?
Run the math first. Add the transfer fee to the new card’s starting balance, simulate payoff at the promo APR over the promo period, then assume the regular APR after. Compare total cost to staying on the current card.
Sources & Methodology
Where we pulled the numbers
- CFPB · Credit cards — CFPB resources on APR, fees, billing, and disputes.
- Federal Reserve · Report to Congress on the Profitability of Credit Card Operations — Official Federal Reserve reporting on credit card pricing and profitability.
- CFPB · Credit card complaint database — Searchable public complaint database used to spot recurring issuer issues.
This guide was created with AI-assisted drafting and human editorial review by Javi Pérez. Figures, examples, and explanations are checked against public sources including CFPB, the Federal Reserve, FDIC, BLS, FTC, and SEC where applicable. Content is reviewed quarterly. Javi Pérez is not a licensed financial advisor, CPA, CFP, loan officer, tax professional, or attorney. This content is educational only and does not replace advice from a qualified professional.
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