Credit Card Interest Calculator
Last updated: July 2026
Estimate monthly interest, payoff time, and total interest for a fixed credit card payment.
Estimated payoff time
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- First month interest: —
- Estimated total interest: —
On this page
Quick summary: Estimate monthly interest, payoff time, and total interest for a fixed credit card payment. Enter the requested values, calculate, review the result, and compare more than one realistic scenario before making a decision.
Read the complete guide
What this calculator does
The Credit Card Interest Calculator estimates interest cost on a revolving balance based on the entered APR and balance assumptions.
How to use the calculator step by step
Enter the balance and APR using the units shown. If the calculator includes days or billing-cycle length, use values that match the account statement.
How the calculation works
A common estimate converts APR into a periodic rate and applies it to the balance. Many issuers use a daily periodic rate based on APR divided by 365, then apply that rate to average daily balance.
Worked example and scenario testing
A 3,000 balance at 24% APR has an approximate monthly interest cost near 60 if the balance remains around 3,000 for the month, though the actual issuer method can differ.
How to interpret your result
Interest cost rises with both the balance and APR. Paying principal earlier generally reduces future interest because less balance remains subject to the rate.
Accuracy, assumptions, and limitations
Grace periods, average daily balance rules, new purchases, cash advances, fees, promotional rates, and compounding conventions can change the real charge.
Common mistakes to avoid
Do not divide APR by 12 and assume the result exactly matches every issuer's billing method. Also distinguish purchase APR from cash-advance or penalty APR.
Privacy and browser-based calculations
Use only general balance and rate figures. Do not enter card numbers or account credentials.