ConverterHub

Credit Card Interest Calculator

Enter the card balance, APR and number of days to get the interest charged.

Result

$47.05
$1.57

How it is calculated

The tool charges simple interest on a fixed balance: interest = balance × (APR / 100) × (days / 365) and daily charge = interest / days. balance is the amount carried, APR is the annual percentage rate in percent (22.9 for 22.9%), and days is how long the balance is carried; if days is left empty, 30 is used. Balance and APR cannot be negative and days must be above zero. Results are shown in USD with two decimals. The calculation assumes the balance stays the same for all those days and does not compound daily, add fees, or subtract payments, so a real statement, where the balance changes and interest is charged on interest, may differ slightly. A card with a grace period charges nothing if paid in full, which this tool does not model.

Worked example

A balance of 2500 carried for 30 days at 22.9% APR. Annual interest: 2500 × 0.229 = 572.50. Share for 30 days: 572.50 × 30 / 365 = $47.05. Daily charge: 47.05 / 30 = $1.57. If you carry the same balance for 60 days, the simple-interest figure doubles to about $94.10.

Try this example →

Common mistakes

  • Entering 0.229 instead of 22.9 for the APR. It is read as 0.229%, which gives pennies of interest.
  • Using a monthly rate as the APR. The tool expects the annual rate and divides by 365 itself.
  • Assuming the balance is constant in real life. New purchases and payments change it, so this is a snapshot for one balance.
  • Ignoring the grace period. If you pay the statement balance in full by the due date, many cards charge no interest at all.
  • Dividing days by 30 or 31 yourself. Enter the actual number of days and the tool applies 365.

Sources

About this calculator

Credit card issuers charge interest based on a daily periodic rate, derived by dividing the card's APR by 365. The interest owed over a billing period is then balance × (APR ÷ 365) × number of days, which is why carrying a balance for even a few extra days meaningfully increases the finance charge.

Because most cards compute interest this way rather than a flat monthly figure, cardholders and financial counselors use this calculation to see exactly how much a balance costs day by day — and to understand why paying down principal early, even mid-cycle, reduces the total interest charged compared to waiting until the statement due date.

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