Credit Card Interest Calculator
Estimate monthly interest using APR and average daily balance, plus projections.
| # | Balance start | Purchases | Interest | Payment | Balance end |
|---|---|---|---|---|---|
| Run a calculation to see the schedule. | |||||
Use this Credit Card Interest Calculator to estimate the interest charged on a carried credit card balance. You can also project how monthly payments and new purchases may affect your balance and total interest over time.
Important: Credit card issuers may use different interest-calculation methods, payment posting rules, and APRs. Use your cardholder agreement or statement for the issuer’s exact calculation.
Credit Card Interest Calculation
This calculator converts the annual percentage rate (APR) into an estimated daily periodic rate:
Daily periodic rate = APR ÷ 100 ÷ 365
The estimated interest for one billing cycle is:
Interest = average daily balance × daily periodic rate × days in billing cycle
If no average daily balance is entered, the calculator uses the current balance as an estimate.
For projections, the balance is updated approximately as:
Ending balance = starting balance + new purchases + interest − payment
This calculation is repeated for the selected number of months.
Example
Suppose your credit card has:
- Average daily balance: $3,500
- APR: 24.99%
- Billing cycle: 30 days
- Monthly payment: $150
- New purchases: $50
The estimated daily periodic rate is:
24.99% ÷ 365 ≈ 0.06847% per day
Estimated billing-cycle interest:
$3,500 × 0.0006847 × 30 ≈ $71.89
The approximate next balance would be:
$3,500 + $50 + $71.89 − $150 = $3,471.89
In this example, the balance falls by only about $28.11 because new purchases and interest consume most of the payment.
Important Notes
- Many credit card issuers calculate interest daily, often using an average daily balance or daily balance method.
- The calculator uses APR ÷ 365. Some issuers may use a different divisor or calculation method.
- Your current balance and average daily balance are not necessarily the same because purchases, payments, refunds, and fees can change the balance during the billing cycle.
- Purchases, cash advances, and balance transfers may have different APRs.
- Payment dates can affect interest when interest accrues daily.
- If your card provides a grace period and you pay the eligible purchase balance in full by the due date, you may avoid interest on those purchases.
- Promotional APRs, penalty rates, fees, daily compounding, and changing payment amounts can make actual results different from the projection.
- Making larger payments and reducing new purchases generally lowers the balance faster and reduces future interest.