A revolving credit card balance keeps accruing interest, and a Credit Card Interest Calculator projects payoff time and total cost today from the balance, APR, and payment entered.
Estimate Credit Card Payoff Time and Interest Cost with a Credit Card Interest Calculator
A Credit Card Interest Calculator projects how long it takes to clear a revolving balance and how much total interest accrues under a chosen payment strategy, including extra monthly payments or ongoing new charges. It is used by cardholders comparing a fixed payment, a target payoff date, or a minimum-payment scenario before deciding how much to pay each month.
Entering Balance, Rate, and Payment Strategy
Inputs include the card balance, APR, a payment strategy — fixed monthly payment, target payoff months, or a minimum-payment estimate — plus ongoing new charges and any extra monthly contribution. The APR is treated as a nominal annual rate applied monthly. Outputs show total interest, payoff time, the first payment’s principal-interest split, and savings from any extra payment.
How Payoff Time, Interest, and the Minimum Payment Estimate Are Calculated
For a fixed payment or a target payoff timeframe, the projection uses the standard amortizing loan payment formula to translate between a monthly payment and a payoff term — the same relationship behind the payoff-time and total-interest disclosure required on credit card statements under Regulation Z, 12 CFR § 1026.7(b)(12), enacted by the CARD Act of 2009.
$$PMT = B \times \frac{r(1+r)^n}{(1+r)^n – 1}$$
B is the current balance, r is the APR divided by 12 and by 100, and n is the number of months. In target-payoff mode, the calculator solves this equation for the payment needed to clear the balance in the chosen number of months; in fixed-payment mode, the same relationship runs the other direction to project payoff time and total interest from a set payment.
The minimum-payment estimate uses the percentage-plus-interest method, which the CFPB describes as the approach most major card issuers use rather than a fixed federal formula: the greater of 1% of the balance plus that month’s interest, or 2% of the balance, with a floor around $25. Actual minimum-payment formulas vary by issuer and card agreement, so this figure is illustrative and should be checked against the cardholder’s own statement.
Once ongoing monthly charges are entered, the payoff can’t be solved with the closed-form formula above: new spending is added to the balance every month before that month’s principal is applied, resetting the base the interest is calculated on. The calculator simulates the balance month by month instead — applying interest, adding new charges, then subtracting principal — until the balance reaches zero.
A frequent input mistake is entering a full desired monthly budget into “Extra Monthly Contribution” instead of only the amount above the planned payment, which double-counts the base payment and overstates how much is actually being paid down each month.
The calculator requires a balance and payment strategy above zero, and allows an APR of 0% for a promotional-rate card, along with non-negative ongoing charges and extra contributions. If the total monthly payment does not exceed that month’s accrued interest plus any ongoing charges, the balance grows without limit instead of reaching zero, and the calculator flags the payment as too low rather than returning a payoff time. The simulation caps at 1,200 months as a ceiling on unrealistic scenarios.
Interest here compounds once a month, at APR divided by 12. Card issuers compound daily instead — a daily periodic rate (APR divided by 365) applied to the average daily balance, per the CFPB — so this monthly figure won’t match a real statement’s finance charge exactly. The tool supports USD, INR, EUR, GBP, AUD, and CAD. Card terms and minimum-payment formulas vary by issuer and country; treat the output as a planning estimate, not a specific card’s contract terms or financial advice.
Visualizing How an Extra Monthly Payment Shortens Payoff Time
Common Questions About the Credit Card Interest Calculator
Why does the calculator ask for “ongoing monthly charges” separately from the balance?
New charges added mid-payoff change the balance interest is calculated on each month, so separating them lets the simulation add that spending back in every cycle instead of assuming the card is never used again.
How is the minimum payment estimated?
It uses the percentage-plus-interest method common among major issuers: the greater of 1% of the balance plus that month’s interest, or 2% of the balance, with a floor around $25. Actual issuer formulas vary.
Why does the calculator sometimes say the payment is too low?
If the total monthly payment doesn’t cover that month’s interest plus any ongoing charges, the balance would grow instead of shrink, so no payoff time exists to calculate.
Does this match the interest shown on an actual statement?
Not exactly. Issuers compound daily, using a daily periodic rate (APR ÷ 365) on the average daily balance; this calculator compounds once a month, so the numbers won’t match exactly.
What happens if the APR is entered as 0%?
All of each payment goes to principal, since there is no interest to amortize, and the payoff time is simply the balance divided by the payment amount.
Which currencies does the calculator support?
US Dollar, Indian Rupee, Euro, British Pound, Australian Dollar, and Canadian Dollar. The math is identical across currencies; only the displayed symbol changes based on the selection.