Credit card interest calculator
Last reviewed · figures computed by the same engine the app runs
Enter a balance, an APR and a monthly payment. The calculator returns how many months until the balance is clear and the total interest you pay to get there. Monthly interest is the balance times the APR divided by 12, rounded to the cent. The daily cost of the same balance is the APR divided by 365. Neither charge hits new purchases while you pay the statement in full and keep the grace period.
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Monthly interest = balance × (APR / 12), rounded to the cent. The payment covers that interest first. Whatever is left reduces the balance. Payoff months are how many times that step runs until the balance is zero, and total interest is the sum. If the payment does not cover the interest, the balance does not clear. This monthly estimate is not the average daily balance method (APR / 365 on each day's balance). Nothing leaves your browser.
How the number is worked out
The daily periodic rate is the APR divided by 365. Some issuers use a 360-day basis, which makes each day marginally more expensive; CardLab supports both.
The rate applies to the balance on each individual day, so a purchase on day 2 is charged for more days than the same purchase on day 28. How average daily balance interest works shows that sum on a 30-day cycle, where moving one payment changes the interest.
The payoff box uses a simpler monthly formula, not that daily sum. Monthly interest equals the balance times the APR divided by 12, rounded to the cent. The payment covers that interest first and the rest reduces the balance. Months are counted until the balance is zero, and total interest is the sum of those monthly charges. If the payment does not cover the interest, the balance never clears and the calculator says so instead of inventing a month count.
None of this applies to new purchases while your grace period is intact. Pay each statement balance in full and those purchases carry no interest at all, whatever the APR says. The rule is on the grace period page and in what is a grace period on a credit card.
The balance and the statement date behind that daily charge belong in the credit card tracker. If the reason you are carrying a balance is rewards, read when cashback loses to interest before you chase the earn rate.
The balance you type is not the figure frozen on the bill generation date, which is the statement closing date. How an APR becomes the daily charge is in APR and interest. To run a full cycle, open the CardLab simulator. Other tools are on the credit card calculators page.
Common questions
How much interest will I pay on a $5,000 credit card balance?
At 24.99% APR, $5,000.00 costs about $3.42 a day, or roughly $102.70 over a 30-day cycle if the balance does not change. Paying $200.00 a month instead clears it in 3 years and costs $2,135.18 in interest on the monthly formula above.
How does this credit card interest calculator work?
Divide the APR by 12. Multiply that monthly rate by the balance and round to the cent. That is one month of interest. Apply the payment to the interest first and the rest to the balance, then repeat until the balance is zero. Payoff months are that count. Total interest is the sum of the monthly interest charges. If the payment does not cover the interest, the balance does not clear. Paying the statement in full keeps the grace period, so new purchases are not charged this interest.
Why was I charged interest when I paid my balance?
Usually residual interest. If you carried a balance last cycle, interest kept accruing between the statement date and the day your payment landed, so a charge appears on the next statement even though you paid in full. Paying in full again clears it and restores the grace period. What each date controls is in statement date vs due date.
Does a 0% APR card really charge no interest?
On the balances the promotion covers, yes, until it expires. Purchases may be excluded if the offer is for balance transfers only, and cash advances are almost never included. Deferred-interest offers are different again: miss the deadline and the whole accrued amount is charged retroactively.