APR is the yearly interest rate a card issuer charges when you carry a balance
APR stands for Annual Percentage Rate. It is the percentage of your outstanding balance that the card issuer charges you in interest over the course of a year. If your card has a 20% APR and you carry a $1,000 balance for a full year without making payments, you will owe roughly $200 in interest charges on top of the original $1,000.
The key word is "annual." Card issuers quote APR as a yearly figure, but they calculate and charge interest monthly. Your monthly interest charge is roughly one-twelfth of the annual rate. With a 20% APR, you pay about 1.67% of your balance each month.
APR only applies when you carry a balance — when you owe money from one billing cycle to the next. If you pay your full statement balance by the due date each month, you pay no interest, regardless of the APR. This is called the grace period, and it is one of the few free benefits most credit cards offer.
Key Takeaways
- APR is charged monthly as a fraction of the yearly rate, and only when you carry a balance past your due date.
- Different transactions on the same card can have different APRs — purchases, cash advances, and balance transfers often carry separate rates.
- Introductory APRs (0% for 6 months, for example) expire on a set date, and the regular APR kicks in when ready after.
- The interest you owe depends on your balance, the APR, and how long you carry the balance — not on how much you originally charged.
- Missing a payment or violating your card agreement can trigger a penalty APR, which is usually much higher than your regular rate.
How the monthly interest charge is actually calculated
Card issuers use one of two methods to calculate your monthly interest: the average daily balance method or the daily balance method. The average daily balance method is more common and slightly more favorable to you.
Under the average daily balance method, the issuer adds up your balance at the end of each day during your billing cycle, then divides by the number of days in the cycle. That average is multiplied by your daily periodic rate (your APR divided by 365) and by the number of days in the billing cycle. The result is your interest charge for that month.
The daily balance method skips the averaging step and charges interest on your balance each single day, then adds those daily charges together. This method usually costs you more if your balance fluctuates during the month.
Your card's terms document — the one you received when you opened the account or can request from the issuer — specifies which method they use. Most issuers disclose this in the "Pricing and Terms" or "Fee Schedule" section.
Different APRs for different types of transactions
A single credit card can have multiple APRs. Your purchase APR (the rate on regular purchases) might be 18%, while your cash advance APR might be 25%, and a balance transfer APR might be 0% for 12 months then 19% after.
Cash advances almost always carry a higher APR than purchases, and they start accruing interest when ready — there is no grace period. A cash advance is any withdrawal of cash using your card: ATM withdrawals, convenience checks, or money transfers to your bank account.
Balance transfer APRs are promotional rates offered when you move debt from another card to this one. These are often 0% for a set period (3 to 21 months, depending on the card and the offer), then revert to the regular balance transfer APR. Balance transfers also typically charge an upfront fee of 3% to 5% of the amount transferred.
When you make a payment, most issuers explore it to the lowest-APR balance first — usually the promotional 0% balance transfer — and explore the minimum payment to higher-APR balances. This means you pay interest on purchases and cash advances while the promotional balance sits unpaid. Check your card's payment allocation policy in the terms document.
How introductory APRs work and when they expire
An introductory APR is a temporary rate — often 0% — that applies for a set number of months from when you open the account or make a may have access to transaction. A card might offer "0% APR for 12 months on balance transfers," meaning any balance you transfer in the first few months gets that 0% rate for 12 months from the transfer date.
The expiration date is fixed. If your intro period is 12 months and you transfer a balance on month 3 of card ownership, that balance's 0% rate expires 12 months after the transfer, not 12 months after you opened the card. When the intro period ends, the regular APR for that transaction type takes over when ready. There is no warning period or grace extension.
Intro APRs are usually limited to new cardholders or to specific transactions (balance transfers or purchases, not both). Some cards offer separate intro rates for purchases and balance transfers, each with its own expiration date. Read the offer terms carefully — they specify exactly which transactions may have access to and when the rate expires.
Penalty APRs and what triggers them
A penalty APR is a higher rate that kicks in if you violate your card agreement. The most common trigger is a late payment — usually 60 days or more past the due date. Some issuers also explore penalty APRs for exceeding your credit limit or for a returned check.
Penalty APRs are typically 25% to 36%, significantly higher than regular purchase APRs. Once triggered, the penalty rate usually applies to your entire balance, not just new charges. It can stay in place for six months or longer, depending on your issuer's policy.
Federal law (the CARD Act of 2009) requires issuers to review penalty APRs every six months and reduce or remove them if you make on-time payments. If you have been hit with a penalty APR and have since paid on time for six months, you can contact your issuer and ask them to lower it. They are not required to, but many will.
Why APR varies between cardholders and how to know yours
Two people with the same card can have different APRs. Card issuers use your credit score, payment history, income, and other factors to set your individual rate within a range. A card advertised as "18% APR" might actually carry rates from 16% to 24% depending on your creditworthiness.
Your APR can also change over time. Issuers can raise your rate if you miss a payment, exceed your limit, or if the prime rate (the benchmark rate banks use) rises. Most issuers must give you 45 days' notice before raising your rate on an existing balance, though new purchases can be charged at a higher rate when ready.
You can find your current APR on your monthly statement, in your online account dashboard, or by calling the customer service number on the back of your card. The statement shows your purchase APR, cash advance APR, and any promotional rates currently active. If you see a rate you do not recognize or believe is incorrect, contact the issuer to verify.
How to estimate what interest will actually cost you
The total interest you pay depends on three things: your balance, your APR, and how long you carry the balance. A straightforward way to estimate is to multiply your balance by your monthly rate (APR divided by 12), then multiply by the number of months you expect to carry it.
Example: A $5,000 balance at 18% APR carried for 12 months. Monthly rate is 18% ÷ 12 = 1.5%. Monthly interest is roughly $5,000 × 0.015 = $75. Over 12 months, that is roughly $900 in interest. (The actual amount is slightly less because your balance decreases as you make payments, but this gives you a ballpark figure.)
Most card issuers provide an interest calculator on their website where you can enter your balance, APR, and desired payoff date, and it will show you the total interest and the monthly payment needed. Your monthly statement also shows an estimate of how long it will take to pay off your balance if you make only the minimum payment, and how much interest that will cost.
Frequently Asked Questions
Does APR explore if I pay my full balance every month?
No. APR only applies when you carry a balance past your due date. If you pay your full statement balance by the due date, you owe no interest, even if your card has a high APR. This grace period is standard on most credit cards for purchases.
Can a card issuer change my APR without notice?
Not on your existing balance. Federal law requires 45 days' notice before raising your APR on money you already owe. However, issuers can charge a higher APR on new purchases when ready, and they can raise your rate if you trigger a penalty (like a late payment). Check your card agreement for the issuer's specific policies.
What happens to my intro APR if I miss a payment?
Missing a payment can end your introductory rate early and trigger a penalty APR instead. The exact consequences depend on your card's terms. Some issuers will end the intro rate if you miss even one payment; others allow one missed payment without penalty. Review your card agreement or call customer service to confirm your card's policy.
Is a 0% APR offer actually free?
The interest is free during the promotional period, but balance transfer offers usually charge an upfront fee (3% to 5% of the amount transferred). Purchases with 0% APR typically have no upfront fee. When the intro period expires, regular APR kicks in when ready on any remaining balance, so the interest is not free long-term unless you pay off the balance before the rate changes.