How Credit Card Interest Is Calculated Each Month

Credit card interest can feel like a mystery number that shows up on your statement. It is actually based on a few simple pieces: your APR, your balance, and how many days are in your billing cycle. Once you see how they fit together, it is much easier to understand your bill and figure out how to pay less interest.

This guide walks through the simple monthly method, then how most cards actually do it day by day, with examples you can follow. To see how interest adds up over time on your own balance, try Savenello's credit card calculator.

Start with your APR

APR stands for annual percentage rate. It is the yearly interest rate on your card. You will find it on your statement, often in a section about interest charges. Many cards have more than one APR, such as one for purchases, one for balance transfers, and a higher one for cash advances.

Because APR is a yearly rate, the card has to turn it into a monthly or daily rate to charge you interest each billing cycle.

The simple method: APR divided by 12

The easiest way to estimate monthly interest is to divide your APR by 12 and apply it to your balance. This is the approach Savenello's calculator uses.

Example (with made-up numbers)

Say you carry a $5,000 balance on a card with a 24% APR.

• 24% ÷ 12 = 2% a month.
• 2% of $5,000 = $100 in interest for the month.

That $100 comes out of your payment first. If you paid $150 that month, only about $50 would go toward the balance itself. This simple method gets you close, which is why it is good for planning.

How most cards actually do it: daily interest

Most cards charge interest daily, using two pieces: a daily periodic rate and your average daily balance.

The daily periodic rate

The daily periodic rate is your APR divided by the number of days in the year. Many cards use 365, and some use 360.

• 24% ÷ 365 = about 0.0658% a day.

The average daily balance

Your balance changes during the month as you make purchases and payments. Instead of using one balance, many cards add up your balance at the end of each day in the billing cycle, then divide by the number of days. That gives your average daily balance.

Example (with made-up numbers)

Say your billing cycle is 30 days. Your balance is $1,000 for the first 15 days, then you make a $500 purchase, so it is $1,500 for the last 15 days.

• Average daily balance: ($1,000 × 15 + $1,500 × 15) ÷ 30 = $1,250.
• Interest: $1,250 × 0.0658% × 30 days = about $24.66.

Using the simple method, $1,250 × 2% = $25.00. The two methods land very close, which is why a monthly estimate works well for planning. Cycles with 31 days, purchase timing, and fees can make your real number a bit different.

When you do not pay interest at all

Most cards offer a grace period. If you pay your full statement balance by the due date, you usually pay no interest on new purchases. Interest generally applies when you carry part of a balance from one month to the next.

If you are deciding how much to pay each month, our guide on minimum payment vs statement balance explains the difference.

Why interest keeps a balance stuck

When you carry a balance, interest is added each month. If your payment is only a little more than that month's interest, the balance barely moves. That is why minimum payments can stretch a balance out for years. Our post on how long it takes to pay off a credit card shows what that looks like over time.

Ways to pay less interest

• Pay the statement balance in full when you can. This usually keeps the grace period and avoids interest on purchases.
• Pay more than the minimum. Anything above that month's interest lowers the balance.
• Pay earlier in the cycle. With the daily method, a lower balance for more days means a lower average daily balance.
• Ask about a lower rate. A lower APR means more of each payment goes to the balance.
• Pause new charges on the card you are paying down.

Savenello shows where your money goes each month so you can find room for extra payments. Connect your bank securely with Plaid.

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Example figures are estimates for illustration only. Your card's actual terms will vary.