Credit Card Interest Calculator
What to do with this number
Your interest charge shows what the balance costs you in one billing cycle. If you only pay the minimum, most of it goes to interest and the balance barely shrinks. Model a payoff plan to see when the debt clears, check what the minimum payment actually covers, or look at the full balance over time to understand how charges and payments interact.
How to Use This Calculator
- 1
Enter your current balance and APR
Use the outstanding balance and the card’s annual percentage rate. If the APR varies, the estimate assumes the rate you enter stays constant.
- 2
Set your monthly payment and any extra payment
Enter the fixed amount you plan to pay each month. Extra Monthly Payment is added to Monthly Payment.
- 3
Review the interest estimate and schedule
The results include total interest, total paid, payoff months, and interest as a percentage of the starting balance. The schedule shows the estimated payment, principal, interest, and remaining balance each month.
Example Calculation
A cardholder has a $5,000 balance at 22% APR and pays $200 each month, with no extra payment.
Current Balance ($)
5,000
APR (Annual Rate) (%)
22
Monthly Payment ($)
200
Extra Monthly Payment ($)
0
Results
Total Interest Paid
$1,749.78
Total Amount Paid
$6,749.78
Months to Pay Off
34 months
Effective Interest Cost
35.0%
Insights card shows the balance and cumulative interest over the payoff schedule.
Tips
The first month adds about $91.67 in interest
At 22% APR, the monthly rate is 22% ÷ 12. Change Monthly Payment to $250 to see how paying more reduces the balance and the interest charged in later months.
A payment must exceed the first month’s interest
For a $5,000 balance at 22% APR, the first month’s interest is $91.67. If Monthly Payment plus Extra Monthly Payment is no higher than that, the calculator reports that the payment is too low to reduce the balance.
Test the rate on a balance-transfer offer
Change APR (Annual Rate) (%) to the offer’s promotional rate and set Extra Monthly Payment to any amount you can reliably pay. Compare the modeled interest with the transfer fee and the rate that applies after the promotion.
What this calculator estimates
Credit card interest is the cost charged on an unpaid balance; this calculator estimates that cost month by month using a fixed APR and payment. It shows the estimated payoff schedule but does not model new purchases, fees, changing rates, or an issuer’s exact daily-balance method.
How the calculation works
Each month, the calculator adds interest to the starting balance and subtracts the payment. The last payment is capped at the remaining balance plus that month’s interest.
Monthly interest = Starting balance × (APR / 12)
Principal paid = Monthly payment − Monthly interest
Ending balance = Starting balance − Principal paid
APR is entered as a percentage and divided by 100 in the calculation. The monthly rate is APR divided by 12. If the scheduled payment exceeds the amount needed to clear the debt, the final payment is reduced.
For the example, the monthly rate is 22% ÷ 12 = 1.8333%. First-month interest is $5,000 × 0.0183333 = $91.67. Of the $200 payment, $200 − $91.67 = $108.33 reduces principal, leaving an estimated balance of $4,891.67. The calculator repeats those steps until the final payment; the resulting schedule has 34 payments and about $1,749.78 in total interest.
How payment size changes interest
A higher payment sends more money to principal after each monthly interest charge. That reduces the balance used to calculate interest in later months.
| Monthly payment | First-month principal reduction | Direction of payoff effect |
|---|---|---|
| $150 | $58.33 | Slowest payoff; most interest |
| $200 | $108.33 | Baseline scenario |
| $250 | $158.33 | Faster payoff; less interest |
The table shows the first month’s arithmetic; use the calculator to generate the full schedule for each payment. The credit card interest savings calculator compares two payment amounts, while the credit card debt reduction calculator estimates savings from adding a regular extra payment.
Interpreting the schedule
Early payments often include more interest because the balance is largest at the start. As principal falls, the same APR produces a smaller interest charge, so more of a fixed payment goes toward principal. The effective interest cost is total interest divided by the original balance; it is not the APR.
If you can pay more than the minimum, compare the added monthly commitment with your need for cash reserves and other high-cost debts. A payment plan that is too aggressive to maintain can lead to new card borrowing when an unexpected expense arrives.
When to use a different calculator
- You want to estimate the required minimum payment → credit card minimum payment calculator
- You want to see the balance after a set period → credit card balance calculator
- You are comparing two payment plans → credit card interest savings calculator
- You are considering a lower-rate transfer offer → balance transfer fee calculator
Why statement interest can differ
This estimate applies a monthly rate to the balance at the start of each modeled month. Issuers generally calculate interest using account terms that can include daily periodic rates, daily balances, and transaction-specific rates. The Federal Reserve’s credit card agreement resources provide official information about card agreements and terms; check your own agreement and statement for the method used on your account.
Frequently Asked Questions
How is monthly credit card interest estimated?
This calculator estimates monthly interest by multiplying the remaining balance by APR divided by 12. Card issuers often calculate interest using a daily periodic rate and average daily balance, so your statement’s exact interest can differ.
How do I calculate credit card payoff interest?
1. Divide APR by 12 and by 100 to get the monthly rate. 2. Multiply the month’s starting balance by that rate to estimate interest. 3. Subtract interest from the payment to find principal paid. 4. Repeat with the new balance until it reaches zero, then add the monthly interest charges.
Why does the final payment differ from my regular payment?
The final payment is reduced to the remaining balance plus that month’s interest. The schedule stops charging the full regular payment once the debt is paid off.
What happens if my payment is less than the interest?
The balance will not decrease if the payment does not cover the interest added for the month. This calculator flags a total payment at or below the first month’s estimated interest as too low to pay down the balance.
Does the estimate include new purchases or late fees?
No, it models one starting balance and fixed payments without new charges, fees, or rate changes. Add those costs to your balance or run a separate scenario to understand their effect.
What should I check before transferring a balance?
Compare the transfer fee, promotional APR period, post-promotion APR, and the monthly payment needed to clear the balance before the promotion ends. The CFPB’s credit card resources explain card costs and repayment considerations.