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Credit Card Interest Calculator

Estimate monthly interest, yearly interest, approximate payoff time and total interest with your preferred currency.

Interactive calculator

See What Your Credit Card Is Really Costing You

Enter your balance, interest rate (APR) and monthly payment to estimate how much interest you could pay and how long it may take to clear your balance.

Monthly Interest£62.50
Yearly Interest£750
Payoff Time--
Total Interest--
Enter your details and press calculate.

This calculator gives approximate estimates only and is not financial advice.

Your Payment Breakdown

This visual shows how the first monthly payment may be split between interest and reducing the balance.

Monthly Payment£150
Interest this month£62.50
Balance reduced£87.50
What this means: Part of your payment covers interest first. The rest reduces the balance.

What this calculator shows

This calculator estimates the cost of carrying a credit card balance. It shows approximate monthly interest, yearly interest, estimated payoff time and the approximate amount of interest you may pay based on the numbers you enter.

Example: A balance of £3,000 at 25% APR could cost around £750 in interest over a year before repayments.

How the calculation works

The calculator uses APR to estimate the monthly interest rate. It then applies that rate to your balance and compares it with your monthly payment to estimate how long repayment could take.

Monthly interest estimate = Balance × APR ÷ 12

Ways to reduce credit card interest

1. Pay more than the minimum.
Even small extra payments can reduce the balance faster.
2. Stop adding new spending.
If the balance keeps growing, repayments may struggle to make progress.
3. Check your APR.
Higher APRs make carrying a balance more expensive.
4. Consider balance transfer costs carefully.
A promotional rate may help, but fees and end dates matter.