Most people know that carrying a credit card balance costs money, but fewer understand exactly how that cost is calculated.
Knowing how interest works can help you avoid unnecessary charges and make better decisions when paying down debt.
Start With the APR
APR stands for annual percentage rate. It’s the yearly interest rate your card charges on balances you carry.
Many cards have more than one APR, such as:
- A purchase APR
- A balance transfer APR
- A cash advance APR, which is often higher
- A penalty APR that may apply after late payments
From Annual Rate to Daily Rate
Although APR is an annual figure, most issuers calculate interest daily. They divide the APR by 365 (or sometimes 360) to get a daily periodic rate.
For example, a 24% APR works out to roughly 0.066% per day.
The Average Daily Balance Method
Many cards use your average daily balance to calculate interest. In simple terms:
- Your balance is recorded at the end of each day in the billing cycle.
- Those daily balances are added up and divided by the number of days.
- The average is multiplied by the daily rate and the number of days in the cycle.
Because interest is often compounded daily, unpaid interest can start earning interest of its own.
How the Grace Period Protects You
Most cards offer a grace period on new purchases. If you pay your full statement balance by the due date, you typically won’t be charged interest on those purchases.
If you carry a balance, though, you may lose the grace period, and new purchases can start accruing interest right away. It may take paying in full for one or more cycles to get it back.
Cash advances usually have no grace period at all.
Ways to Pay Less Interest
- Pay the full statement balance whenever possible
- If you can’t, pay as much above the minimum as you can
- Make payments earlier in the cycle to lower your average daily balance
- Avoid cash advances
- Always pay on time to avoid a penalty APR
Final Takeaway
Credit card interest is calculated daily and can grow quickly when balances are carried from month to month. Understanding your APR, the grace period, and how your balance is measured puts you in a better position to keep costs low.
The simplest way to avoid interest is to pay your statement balance in full and on time.
