Credit Card Interest Calculator

See exactly how much interest you'll pay and how long it will take to pay off your credit card balance.

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Enter your values and click Calculate

This credit card interest calculator shows you the true cost of carrying a credit card balance. Enter your current balance, annual percentage rate (APR), and monthly payment to see how many months until payoff, total interest paid, total amount paid, and what percentage of your original balance goes to interest charges. Credit card interest compounds monthly — your APR is divided by 12 to get a monthly rate, applied to the outstanding balance each month before your payment is credited. This means minimum payments, which are typically 1–2% of the balance, can drag out payoff periods for decades and multiply the cost of purchases several times over. The calculator also warns when a monthly payment barely covers the interest charge — a situation where the balance barely decreases even with consistent payments.

How It Works

Monthly interest rate = APR ÷ 12 ÷ 100. Each month: interest charge = remaining balance × monthly rate. New balance = old balance + interest charge − monthly payment. This repeats until the balance reaches zero. The calculator iterates month by month rather than using a closed-form formula, which correctly handles the final partial payment. A warning is shown if the monthly payment does not exceed the first month's interest charge — in that case the balance grows indefinitely rather than being paid off. Total interest = sum of all monthly interest charges. Interest as a percentage of original balance = total interest ÷ original balance × 100.

Examples

Minimum Payment Trap
$5,000 balance at 24.99% APR, paying minimum $100/month.
Result: Takes approximately 109 months (9 years), total interest ~$5,800 — more than the original balance.
Aggressive Payoff
$5,000 balance at 24.99% APR, paying $300/month.
Result: Paid off in approximately 20 months, total interest ~$1,300.
Low APR Balance Transfer
$8,000 balance at 5.99% APR (post-transfer), paying $250/month.
Result: Paid off in approximately 35 months, total interest ~$697 — a fraction of what high-APR cards charge.

Frequently Asked Questions

How is credit card interest calculated?
Credit card interest is calculated using your Average Daily Balance (ADB) method in most cases — the average balance across all days in the billing cycle is multiplied by the daily periodic rate (APR ÷ 365) and then by the number of days in the cycle. This calculator uses a simplified monthly rate (APR ÷ 12) applied to the beginning balance each month, which gives a very close approximation of actual interest charges. The exact amount will vary slightly based on your card's specific calculation method and when you make payments.
What is a good APR for a credit card?
The average credit card APR in the US was approximately 21–22% in 2026. A 'good' APR depends on your credit profile: excellent credit (750+) typically qualifies for 15–18% APR; good credit (700–749) qualifies for 18–22%; fair credit pays 22–27%+; poor credit may face 27–36% or be limited to secured cards. Rewards cards often carry higher APRs. If you carry a balance, APR is one of the most important factors in card selection — if you pay in full monthly, the APR is irrelevant since you pay no interest.
Should I pay more than the minimum payment?
Almost always yes — the difference is dramatic. On a $5,000 balance at 24.99% APR, paying $100/month (roughly minimum) takes 9 years and costs $5,800 in interest. Paying $300/month takes 20 months and costs $1,300 in interest — saving $4,500 and 7 years. Even adding $50/month to minimum payments dramatically accelerates payoff. The credit card minimum payment is designed by card issuers to maximize long-term interest income — it is not designed to help you become debt-free quickly.
Is a balance transfer worth it?
A 0% introductory APR balance transfer can save significant money if you pay off the balance before the promotional period ends (typically 12–21 months). Balance transfer fees are usually 3–5% of the transferred amount — compare this to the interest you'd pay staying on the original card. For example, transferring $5,000 with a 3% fee costs $150 upfront but saves you $1,000–$2,000+ in interest if you pay it off during the promo period. Avoid making new purchases on a balance transfer card — new purchases often accrue interest immediately at the regular APR.