How to Calculate Credit Card Interest

If you have a credit card, you may know that interest is added to your balance until you pay it off. However, you may not understand what each of the terms surrounding interest rates means. You’ll hear words like annual percentage rate (APR), daily interest rate, and average daily balance.

credit card statement

So, how exactly does credit card interest work? It can be quite confusing what each term means and how much interest you are actually paying on your credit card debt. This article explains how credit card interest is calculated and added to your balance.

What is the annual percentage rate?

When comparing credit cards, you’ll notice that one of the most common terms used is annual percentage rate or APR. For example, one credit card may have an APR of 15%, while another may say it has an APR of 24%. This term can be confusing because interest is added to your balance each month rather than once a year.

The APR is the total daily periodic rate multiplied by the number of times the interest is compounded in a year. It includes interest and any fees charged to the account. It’s governed by the Truth in Lending Act. This federal law ensures information is disclosed to the borrower to prevent deceptive practices by the credit card company or lender.

How is credit card interest calculated?

For credit cards, the interest rate is calculated on a daily basis. So, you can discover your daily rate based on the APR advertised with your credit card. You just have to divide the APR by 365, the number of days in one year.

If your credit card has an APR of 15%, the rate is 0.041% per day. If the rate is 24%, the daily rate becomes 0.088%. This may seem like such a small amount until you realize that it adds up over time as long as you carry a balance on your credit card.

Depending on which card you have, APRs may differ for different kinds of transactions, such as purchases, cash advances, and balance transfers.

What is average daily balance?

The interest charged to your account is calculated based on the amount you owe. This means that the credit card issuer figures the average balance you carried for the entire month. If you made a payment on your balance, it is figured in, so you are not charged interest on the entire balance over the month.

To figure your average daily balance, you must know your exact balance for each day. Say you have a balance of $2,000, and you make a payment where $500 goes to the balance in the middle of the month (day 15). Your average daily balance is calculated as follows: [(15 x $2,000) + (15 x $1500)]/30 = $1750.

This suggests that the more you pay off your balance, and the sooner you make the payment, the more you save in interest charges. A person who makes their payment early in the month will be charged less than someone who waits until the last day. It’s important to understand that the term month may not be the same as a calendar month.

For a credit card, the month begins whenever the billing cycle ends. If your statement cuts on the 15th, the daily balance begins calculating on the 16th. It doesn’t really matter when the billing cycle begins because it is still calculated daily. It’s added monthly to your balance, but it can help you understand how your interest is calculated and when.

Put the Numbers Together

To know how much credit card interest you are charged in a month, you would multiply the answer you got for your average daily balance by the daily interest rate. Then, take that answer and multiply it by the number of days for that month.

If you have an average balance of $700 with a daily interest rate of 0.088% from the 24% APR, you will pay $18.48 for the month. That doesn’t sound like a lot, but in a year, you would be paying $221.76 per year in interest. So instead of spending $700 on those items charged to that card, they’ve actually cost you $921.76.

Compounded Interest

Credit card issuers don’t charge simple interest. Instead, they compound it so that you are paying interest on interest. Each month that you have a balance, they add interest from it to the balance. So, the next month, you are paying interest on the entire balance, which includes last month’s interest.

In the example above, you would pay interest on $718.48 if you made no payments. Therefore, your interest for that month would be $18.96. Not much more, but an increase from the previous month.

Looking at the information above, you can see how carrying a credit card balance can be detrimental to your overall budget. If you don’t pay more than the required minimum monthly payment, you won’t pay off your balance very quickly, which means the interest continues to add up.

This puts money in the pocket of the credit card companies instead of your own. If you can even pay $20 or $50 extra each month, you’ll reduce the amount of interest you pay. This means more of your monthly payment will go towards the outstanding balance.

See also: Simple Interest vs. Compound Interest

How Credit Card Interest Rates are Determined

When comparing credit cards, you’ll notice some carry a higher rate than others. So, how exactly do credit card companies determine what interest rate to charge? Several factors impact the rate, including your credit history.

The interest rate is the amount of risk the credit card issuer carries by extending credit to you. Someone with a good to excellent credit score can often obtain a credit card with a lower interest rate than someone with poor credit.

Rewards cards also come with a higher APR to compensate for the benefits they provide. Of course, you may be able to find an exception to the rule if you do enough research. To qualify for a credit card with a lower interest rate, maintain a good credit score. If yours needs work, focus on improving your credit, and in a year or two, you’ll get offers for credit cards with better rates.

How to Avoid Paying Credit Card Interest

Most credit cards offer a 25- to 30-day grace period. If you pay your credit card bill in full before this time, you won’t be charged interest on your purchases. Paying your balance in full before your due date is the best way to avoid paying interest entirely.

So, to avoid interest charges on your purchases, all you have to do is pay your balance on time and in full every month. By doing so, you’ll never have to pay credit card interest charges. In addition, if you have a rewards credit card, you can actually come out ahead with cashback or airline miles.

Bottom Line

You don’t need to know the details of how to calculate credit card interest to pay your credit card bills. However, it does help to give you an understanding of what you’re paying each month. Once you realize how interest rates work and all the terms associated with them, you’ll be more aware of the true cost of the purchases you make.

You’ll also better understand exactly what you’re paying when you make your payments each month. Simply knowing about interest and seeing the figures can help you manage your budget better and be more dedicated to paying off a balance as quickly as possible.

The next time you get your credit card statement, calculate the interest on your own. Then, estimate what you will pay the following month to see how it impacts your situation. This process can help you make important decisions about your finances.

Lauren Ward
Meet the author

Lauren is a personal finance writer who strives to equip readers with the knowledge to achieve their financial objectives. She has over a decade of experience and a Bachelor's degree in Japanese from Georgetown University.