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Credit-card interest is the cost of carrying a balance under the terms of a card agreement. The annual percentage rate, or APR, expresses the annualized interest rate, but the dollar amount you pay depends on balance, timing, compounding method, fees, and whether a grace period applies.
APR is not the same as a monthly interest charge
A card may advertise an APR, but issuers generally calculate interest using periodic rates and account balances under the card agreement. The exact method is disclosed in the terms.
Average daily balance
Many cards use an average daily balance method. The issuer tracks balances during the billing cycle, calculates an average, and applies the periodic rate. Making a payment earlier can therefore reduce the balance exposed to interest.
Grace periods
CFPB explains that a grace period is the time between the end of a billing cycle and the payment due date. Cards are not required to offer a grace period, but when one applies to purchases, paying the statement balance in full can avoid purchase interest.
What happens when you carry a balance
If you do not pay in full, interest can continue accruing on the unpaid balance. Depending on the agreement, new purchases can also lose the grace period until qualifying conditions are restored.
Minimum payments
Paying only the minimum keeps the account from being immediately past due, but it can extend repayment for years and greatly increase interest cost. Card statements include a minimum-payment warning showing how long repayment may take under stated assumptions.
Variable APRs
Many cards have variable APRs tied to a benchmark such as the prime rate plus a margin. When the benchmark changes, the APR can change according to the agreement.
Penalty APRs and fees
Late payments can trigger fees and, under applicable terms and law, may affect the APR. Cash advances and balance transfers can have separate APRs and fees.
A simple payoff strategy
- Stop adding new revolving balances if practical.
- Pay at least the required minimum on time.
- Direct extra money to the highest-rate debt if minimizing interest is the priority.
- Track promotional-rate expiration dates.
- Compare consolidation only after including fees and total repayment cost.
Use the calculator
EconomicHQ’s Debt Payoff Calculator can model how payment size and interest rate affect payoff time.
Continue learning
Read APY vs. APR and Debt Snowball vs. Debt Avalanche.
Sources & methodology
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Sources, dates, and methodology matter.
EconomicHQ prioritizes primary sources for consequential financial and economic claims and identifies reporting periods for changing information. This article is educational and does not provide individualized financial, investment, tax, legal, or credit advice.