Assumptions
- The APR and fixed monthly payment remain constant.
- No purchases, transfers, fees, credits, or missed payments occur.
- Interest is modeled monthly rather than with an issuer-specific daily method.
Credit card interest calculator
Estimate the interest cost of your card payoff
A credit card payment covers both interest and principal, so the total cost is larger than the starting balance. Enter a balance, APR, and fixed monthly payment to estimate interest across the full payoff timeline.
Private by design
Your financial values stay in this browser.
No account required
No signup, bank connection, or credit pull.
Deterministic math
The same inputs produce the same estimate.
Calculate locally
Calculate estimated card interest
Use the current card balance and APR with the fixed amount you plan to pay every month.
Credit card interest calculator
Estimate your credit card interest cost
See the estimated interest charged while you repay one credit card balance.
Understand the output
Your estimated interest cost
The result prioritizes total estimated interest and total paid, then shows the payoff date, months remaining, and monthly interest charges.
Methodology and limits
How this calculator estimates payoff
The engine applies APR divided by 12 to each opening monthly balance, rounds interest to cents, and then applies the fixed payment.
The process repeats until the amount due is zero. The final payment is capped so the model never pays more than the remaining amount.
Limitations
- The estimate can differ from statement interest because issuers often accrue daily.
- The calculator does not estimate interest for revolving purchases with changing balances.
Methodology reviewed August 26, 2026. Results are educational planning estimates, not financial advice or lender payoff quotes.
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