How the Credit Card Interest Calculator works
Estimate monthly and annual credit card interest. Adjust the inputs above, then use the calculate button to generate a fresh estimate based on the numbers you entered.
The result is designed to give you a quick planning number, plus a short breakdown of the major figures behind it. You can reset the form at any time and try a different scenario.
When to use this calculator
Use this credit card interest calculator to estimate how much interest a revolving card balance may generate. It is helpful for seeing the cost of carrying a balance and testing how a higher payment changes the result.
Formula
Monthly interest = balance x APR / 12
- Balance is the current credit card amount owed.
- APR is converted into an estimated monthly rate.
- Monthly payment reduces the balance after interest is added.
Worked example
For a $6,000 balance at 21.99% APR with a $250 monthly payment, the calculator estimates monthly interest and how interest changes as the balance falls.
Common mistakes
- Assuming APR is charged only once per year.
- Ignoring new purchases, cash advances or late fees.
- Making payments too low to reduce the balance quickly.
FAQs
Is APR the same as the monthly interest rate?
No. APR is annual, so this estimate divides it into a monthly rate.
Why does interest fall as I pay down the card?
Interest is based on the remaining balance, so a lower balance usually means less interest.
Does this include grace periods?
No. It is designed for balances that are being carried and accruing interest.