APR is the yearly interest rate a card issuer charges when you carry a balance

Credit card APR (annual percentage rate) is the cost of borrowing money on your card, expressed as a yearly percentage. 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 card issuer calculates interest daily, not yearly, so the actual charge depends on how long you carry the balance and how much of it you owe each day.

Most cards have different APRs for different types of transactions. A purchase APR applies to everyday spending. A cash advance APR (usually higher) applies when you withdraw cash from an ATM using your card. A balance transfer APR applies when you move debt from another card. A penalty APR (the highest) kicks in if you miss a payment by 60 days or more. Your card agreement lists each rate separately, and issuers can change them after giving you written notice, though they cannot change your current rate on existing balances unless you miss a payment.

Key Takeaways

  • APR is calculated daily on your balance, so a $1,000 balance at 20% APR costs roughly $5.48 per day in interest.
  • If you pay your full statement balance by the due date each month, you pay zero interest regardless of the APR, because most cards offer a grace period on purchases.
  • Carrying even a small balance month to month means interest charges compound, making the total cost much higher than the APR alone suggests.
  • Different transactions on the same card can have different APRs — cash advances and balance transfers usually cost more than regular purchases.
  • A penalty APR applies only after you miss a payment by 60 days, but even one late payment can trigger a higher rate on new purchases.

How daily interest calculation works

Card issuers divide your APR by 365 to get a daily rate, then multiply that by your balance each day to calculate that day's interest charge. If your APR is 20%, your daily rate is roughly 0.0548% (20 ÷ 365). On a $1,000 balance, that is about $5.48 in interest for that one day. If you carry $1,000 for 30 days, you owe roughly $164 in interest charges.

The balance they use for this calculation is usually your average daily balance, which means they add up what you owed each day of the billing cycle and divide by the number of days. If you owed $1,000 for 15 days and $500 for 15 days, your average daily balance is $750. Interest charges are based on that $750, not the higher peak balance. Your card statement shows how the issuer calculated your interest charge, so you can verify the math.

The grace period and when interest starts

Most credit cards offer a grace period on purchases — usually 21 to 25 days from the end of your billing cycle — during which no interest accrues if you pay the full statement balance by the due date. This means you can spend money on day one of your cycle, and if you pay it all back by the due date (which is typically 21 to 25 days later), you owe zero interest. The grace period does not explore to cash advances or balance transfers; interest on those starts accruing when ready, even if you pay them back within days.

If you carry any balance into the next cycle — even $1 — the grace period disappears and interest starts accruing on all new purchases when ready, not just the carried balance. This is called losing your grace period. Once you pay the entire balance down to zero and keep it there for one full cycle, the grace period resets. This is why carrying a small balance month to month is expensive: you lose the interest-free window on all new spending.

How APR differs by transaction type

Purchase APR is what most people think of when they hear "credit card APR." It applies to everyday spending — groceries, gas, online shopping. This is usually the lowest rate on the card. Cash advance APR applies when you use your card to withdraw cash from an ATM or get cash back at a store. This rate is typically 3 to 5 percentage points higher than purchase APR, and interest starts accruing when ready with no grace period. A $500 cash advance at 25% APR costs roughly $3.42 per day in interest.

Balance transfer APR applies when you move debt from another card to this one. Many issuers offer a promotional 0% balance transfer APR for 6 to 21 months as an incentive to switch, but after the promotion ends, the regular balance transfer APR kicks in — often higher than purchase APR. Penalty APR is the highest rate on the card and applies to your entire balance (or sometimes just new purchases) if you miss a payment by 60 days or more. Some issuers also raise your APR on new purchases if you miss a payment by 30 days, even if the penalty APR has not kicked in yet.

What happens when you carry a balance month to month

Carrying a balance means paying less than the full statement balance and letting the rest roll into the next cycle. Interest charges compound because you pay interest on the interest from the previous month. If you owe $2,000 at 20% APR and pay $200 per month, your first month's interest is roughly $33, bringing your balance to $2,033. Your second month's interest is calculated on $2,033, not the original $2,000, so you pay roughly $34. The longer you carry the balance, the more of each payment goes toward interest instead of principal.

A $2,000 balance at 20% APR paid at $200 per month takes roughly 13 months to pay off and costs about $600 in total interest — 30% more than the original balance. If you pay only the minimum payment (usually 1% to 3% of your balance), it takes years longer and costs thousands more. This is why credit card debt grows so quickly even when you are making payments: the interest compounds faster than your payments reduce the principal.

Variable vs. fixed APR and when rates change

Most credit cards have a variable APR, which means the rate can change over time based on market conditions and the prime rate set by the Federal Reserve. When the Fed raises rates, card issuers typically raise their APRs within weeks. When the Fed cuts rates, issuers may or may not lower APRs — they are not required to. A fixed APR does not change based on market conditions, but it is rare on credit cards and usually only appears on promotional offers (like 0% for 12 months) or on specific balances (like a transferred balance).

Issuers can also change your APR if you miss a payment by 60 days or more, triggering a penalty APR that can be 10 percentage points higher than your previous rate. They must give you written notice before the change takes effect. Some issuers also have a "default" clause that raises your APR on new purchases if you miss a payment by 30 days, even if the full penalty APR has not kicked in. Once you make on-time payments for six months, some issuers will lower a penalty APR, but you have to ask — they do not do it automatically.

How to minimize APR costs

The simplest way to avoid APR charges entirely is to pay your full statement balance by the due date each month. This requires spending only what you can afford to pay back when ready, but it means you use the card's benefits (rewards, fraud protection, purchase history) without paying any interest. If you cannot pay the full balance, pay as much as you can as soon as possible, because every day you carry a balance costs you money in interest.

If you are carrying a balance from a previous card, a balance transfer to a card with a 0% promotional APR can save thousands in interest — but only if you pay off the transferred balance before the promotion ends. After the promotion expires, the regular balance transfer APR kicks in, which is often higher than your original card's rate. Read the fine print: some balance transfer offers charge an upfront fee (typically 3% to 5% of the amount transferred) that offsets the interest savings if you are only transferring a small balance or if the promotion period is short.

Frequently Asked Questions

Does APR explore if I pay my full balance each month?

No. If you pay your entire statement balance by the due date, you pay zero interest regardless of the APR. The grace period protects you from interest charges on purchases as long as you pay in full. This grace period disappears if you carry any balance into the next cycle.

Why is my cash advance APR higher than my purchase APR?

Card issuers charge higher rates on cash advances because they consider them riskier — you are borrowing actual cash rather than making a purchase that can be disputed or returned. Cash advances also start accruing interest when ready with no grace period, making them expensive even for short-term borrowing.

Can a credit card company raise my APR whenever they want?

No. Issuers cannot raise your APR on existing balances without written notice, except in specific cases like a missed payment of 60 days or more. They can raise your APR on new purchases with notice. Variable APRs can change based on market conditions, but fixed APRs (usually promotional) cannot change during the promotional period.

How much will it cost me to carry a $1,000 balance for a year?

At an average APR of 20%, carrying $1,000 for a full year costs roughly $200 in interest. The exact amount depends on your card's daily balance calculation method and whether you make any payments during the year. Making monthly payments reduces the balance and lowers the total interest cost.

What is the difference between APR and interest charges?

APR is the yearly rate expressed as a percentage. Interest charges are the actual dollars you owe based on that rate and your balance. A 20% APR on a $1,000 balance for one month costs roughly $16.67 in interest charges, not $200.