Credit Card Interest Calculator
Estimate the interest charged on a credit card balance for a billing cycle using the daily periodic rate, as most US card issuers do.
For information and education only — not financial advice. Results are estimates based on the numbers you enter; check important decisions with a qualified professional.
How to use
- 1Enter your average daily balance, APR and the days in the billing cycle.
- 2See the interest for the cycle and per day.
How it's calculated
Daily periodic rate = APR ÷ 365. Interest = average daily balance × daily rate × days in cycle. (Some issuers use 360 days or compound daily; results differ by cents.)
Frequently asked questions
How do I avoid credit card interest?
Pay the full statement balance by the due date each month. Most cards then charge no interest on purchases (the grace period).
What is the average daily balance?
The balance at the end of each day in the cycle, added up and divided by the number of days. Your statement often lists it.
Why is interest charged on new purchases?
If you carried a balance from last month, you usually lose the grace period, so new purchases accrue interest from the day you make them.