One of the most important factors in choosing a credit card is its interest rate, and it’s also important to know how to calculate credit card interest. All credit cards must disclose their annual percentage rate, or APR, which expresses their interest rates in a single annual number. Almost all credit cards charge interest only on balances that you don’t fully pay off in the most current billing cycle. But how does APR translate into the amount of interest you’ll actually pay?
Read on to learn more about, including an in-depth look at how you can find your daily periodic rate, simple versus compound interest, how to calculate your average daily balance, and more. Or skip ahead to learn how your APR is calculated or to compare the best balance transfer offers to avoid paying interest.
Step 1: Divide APR by 360 (or 365) to Find Out Your Daily Periodic Rate
Before we can explain the first step, we should clarify a few important terms:
Grace Period: The normal billing cycle for a credit card can range from 28 to 31 days. The due date for your monthly payment is no less than 21 days after the end of the billing cycle. Each billing cycle provides a grace period, which means you don’t incur interest on purchases made within the billing cycle if you pay them in full by the due date. Your outstanding balance is the accumulated amount you haven’t paid within a grace period.
Simple Versus Compound Interest: Simple interest is the amount you pay on your outstanding balance without including the effect of compounding. Virtually all cards figure your interest with compounding, which means they add the interest you already owe to the amount subject to interest – you are paying interest on interest.
In the good old days, credit cards used monthly compounding, but the current fashion is daily or continuous compounding, which will cost you more. As an example of daily compounding, if your outstanding balance is $1,000 and the day’s interest is 71 cents, then tomorrow’s outstanding balance will be $1,000.71 (assuming no other purchases or payments).
Nominal Versus Effective APR: When you see an ad for a credit card, the interest rate is expressed as the nominal APR, which is based on simple interest and excludes fees. The more appropriate number is the effective APR, which includes the effects of compounding and any fees that are not paid separately. Some cards charge the annual fee (if any) as a lump sum, but others spread the annual fee over the entire year, making it part of the effective APR.
If possible, obtain the effective APR of any credit card you are considering. Fees for late payments or for exceeding your credit limit are not included in any APR, since they are charged separately.
To illustrate the three-step process for calculating your interest charges, imagine that you have an outstanding balance of $3,500 on a credit card with an interest rate of 25 percent.
In this example, the credit card uses a 360-day year (some cards use 365, terms will vary), so the daily percentage rate, or DPR, is equal to 25% / 360, or .06944%. This is the interest rate you pay each day on the balance subject to interest. Assuming daily compounding and no other activity, your daily balance would grow each day by the interest charged on the previous day.
Step 2: Calculate Your Average Daily Balance
The average daily balance is computed by adding together each day’s outstanding balance and dividing by the number of days in the billing period. For simplicity’s sake, we set the average daily balance to $3,500.
Step 3: (Avg. Daily Balance x DPR) x Days in the Month
Finally, we calculate the interest charged for the billing cycle, which in this example, is $3,500 x .06944% x 30 days, or $72.91. This is the amount of interest you would be charged on a card with a $3,500 balance and a 25% interest rate.
How Banks Determine Your APR
The APR on your credit card is based on the bank’s opinion of your creditworthiness, which is in large part derived from your credit score. Most banks use FICO credit scores, which range from 300 (the worst) to 850 (the best).
Each of the three major credit bureaus, Equifax, Experian, and TransUnion figure their FICO scores a little differently, but the scores tend to cluster closely. Interpretations differ, but generally, 700 is considered the dividing line between good and fair scores. The lower the score, the higher APR you’ll pay. If your score is too low, you could have difficulty qualifying for any credit at all.
Sometimes, banks will take into account other factors when determining your APR, such as black marks on your credit history (bankruptcies, court decisions, garnished wages, etc.). You will save money on interest if you can raise your FICO score – check out the myFICO website for tips on how to do that.
Delay Interest Payments with a Balance Transfer Offer
Many credit cards offer special balance transfer deals that can save you money. In a balance transfer, you move your outstanding balance from one credit card to another. To entice new customers, the balance transfer offers usually include a set number of months during which you don’t owe any interest on the transferred amount.
Some of the best balance transfer offers grant interest-free periods of 15 or even 21 months. In addition, some cards will also grant a multi-month grace period on new purchases made after you transfer a balance. If you combine that with a zero-percent annual fee and a reasonably low APR, you have the makings of a great credit card. Here are some of our favorites:
- INTRO OFFER: Unlimited Cashback Match – only from Discover. Discover will automatically match all the cash back you’ve earned at the end of your first year! There’s no minimum spending or maximum rewards. You could turn $150 cash back into $300.
- Earn 5% cash back on everyday purchases at different places each quarter like Amazon.com, grocery stores, restaurants, and gas stations, up to the quarterly maximum when you activate. Plus, earn unlimited 1% cash back on all other purchases – automatically.
- Discover could help you reduce exposure of your personal information online by helping you remove it from select people-search sites that could sell your data. It’s free, activate with the mobile app.
- Every $1 you earn in cash back is $1 you can redeem.
- No annual fee.
- Click through to Discover’s website to see terms and conditions.
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Intro (Purchases)
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Intro (Transfers)
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Regular APR
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Annual Fee
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Credit Needed
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|---|---|---|---|---|
0% Intro APR for 6 months
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0% Intro APR for 18 months
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16.99% - 27.99% Variable APR
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$0
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Excellent/Good
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- 0% Introductory APR for 21 billing cycles for purchases, and for any balance transfers made in the first 60 days. After the intro APR offer ends, 15.99% - 25.99% Variable APR will apply. A 3% fee applies to all balance transfers.
- No annual fee.
- No penalty APR. Paying late won't automatically raise your interest rate (APR). Other account pricing and terms apply.
- Access your FICO® Score for free within Online Banking or your Mobile Banking app.
- Contactless Cards - The security of a chip card, with the convenience of a tap.
- This online only offer may not be available if you leave this page or if you visit a Bank of America financial center. You can take advantage of this offer when you apply now.
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Intro (Purchases)
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Intro (Transfers)
|
Regular APR
|
Annual Fee
|
Credit Needed
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|---|---|---|---|---|
0% Intro APR for 21 billing cycles for purchases
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0% Intro APR for 21 billing cycles for any balance transfers made in the first 60 days
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15.99% - 25.99% Variable APR on purchases and balance transfers
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$0
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Excellent/Good
|
Additional Disclosure: Bank of America is a CardRates advertiser.
- No Late Fees, No Penalty Rate, and No Annual Fee... Ever
- 0% Intro APR for 21 months on balance transfers from date of first transfer and 0% Intro APR for 12 months on purchases from date of account opening. After that the variable APR will be 18.99% - 29.74%, based on your creditworthiness. Balance transfers must be completed within 4 months of account opening.
- There is an introductory balance transfer fee of $5 or 3% of the amount of the transfer, whichever is greater for balances transfers completed within 4 months of account opening.
- Stay protected with Citi® Quick Lock
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Intro (Purchases)
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Intro (Transfers)
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Regular APR
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Annual Fee
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Credit Needed
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|---|---|---|---|---|
0% Intro APR Period 12 months on Purchases
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0% Intro APR Period 21 months on Balance Transfers
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18.99% - 29.74% (Variable)
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$0
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Excellent, Good Credit
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Additional Disclosure: Citi is a CardRates advertiser.
- 0% Intro APR for 21 months on balance transfers from date of first transfer and 0% Intro APR for 12 months on purchases from date of account opening. After that the variable APR will be 17.99% - 28.74%, based on your creditworthiness. Balance transfers must be completed within 4 months of account opening.
- There is a balance transfer fee of either $5 or 5% of the amount of each transfer, whichever is greater
- Get free access to your FICO® Score online.
- With Citi Entertainment®, get special access to purchase tickets to thousands of events, including concerts, sporting events, dining experiences and more.
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Intro (Purchases)
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Intro (Transfers)
|
Regular APR
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Annual Fee
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Credit Needed
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|---|---|---|---|---|
0% 12 months on Purchases
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0% 21 months on Balance Transfers
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17.99% - 28.74% (Variable)
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$0
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Excellent, Good
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Additional Disclosure: Citi is a CardRates advertiser.
- $200 online cash rewards bonus after you make at least $1,000 in purchases in the first 90 days of account opening.
- Earn 3% cash back in the category of your choice, automatic 2% at grocery stores and wholesale clubs (up to $2,500 in combined choice category/grocery store/wholesale club quarterly purchases) and unlimited 1% on all other purchases.
- If you're a Preferred Rewards member, you can earn 25%-75% more cash back on every purchase. That means you could earn 3.75%-5.25% cash back on purchases in your choice category.
- No annual fee and no expiration on rewards.
- 0% Introductory APR for 18 billing cycles for purchases, and for any balance transfers made in the first 60 days. After the intro APR offer ends, 17.99% - 27.99% Variable APR will apply. A 3% fee applies to all balance transfers.
- Contactless Cards - The security of a chip card, with the convenience of a tap.
- This online only offer may not be available if you leave this page or if you visit a Bank of America financial center. You can take advantage of this offer when you apply now.
|
Intro (Purchases)
|
Intro (Transfers)
|
Regular APR
|
Annual Fee
|
Credit Needed
|
|---|---|---|---|---|
0% Intro APR for 18 billing cycles for purchases
|
0% Intro APR for 18 billing cycles for any balance transfers made in the first 60 days
|
17.99% - 27.99% Variable APR on purchases and balance transfers
|
$0
|
Excellent/Good
|
Additional Disclosure: Bank of America is a CardRates advertiser.
+See more balance transfer cards
Pay Your Balance in Full to Avoid Interest Altogether
Now that you know how interest is calculated, you can follow this strategy to lower your interest expenses:
- Improve your credit score
- Shop around for a credit card that combines the lowest effective APY with the best balance transfer program
- Transfer debt from other credit cards to your new one
- Pay down your credit card debt during the 0% interest intro period of your balance transfer
- Avoid accumulating outstanding balances in the future
For almost all credit cards, you’d never shell out any interest if you paid off your balance in full each month. However, some credit cards do not provide grace periods, so it’s worth the extra effort to look into this before applying. One other point – cash advances incur interest immediately and never have a grace period, so if you’re looking to avoid interest, that may not be the route for you.
Advertiser Disclosure
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Editorial Note: Our site content is not provided or commissioned by any credit card issuer(s). Opinions expressed on CardRates.com are the author's alone, not those of any credit card issuer, and have not been reviewed, approved, or otherwise endorsed by credit card issuers. Every reasonable effort has been made to maintain accurate information; however, all credit card offer details, including information about rewards, signup bonuses, introductory offers, and other terms and conditions, is presented without warranty. Clicking on any offer on CardRates.com will direct you to the issuer's website, where you can review the current terms and conditions of the offer.
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