APR stands for Annual Percentage Rate. It is the yearly interest rate your credit card charges on balances you carry past the due date. If you pay your full balance every month, your APR is irrelevant - you will never pay a cent in interest. If you carry a balance, APR is the single most expensive feature of your card.
How Interest Actually Compounds
Credit card interest is not calculated annually - it compounds daily. Your card takes your APR, divides by 365 to get a daily rate, and applies that to your balance every day. A 22% APR means a daily rate of 0.0603%. On a $1,000 balance, that is $0.60 per day, $18.50 per month, and $220 per year - if the balance stays constant. But since interest is added to the balance, you are paying interest on interest.
Types of APR
- Purchase APR - The standard rate for purchases. Typically 18-28% depending on your credit score.
- Cash advance APR - Rate for ATM withdrawals or cash-like transactions. Usually 25-30% with no grace period - interest starts immediately.
- Balance transfer APR - Rate for balances transferred from other cards. Often 0% for 12-21 months as a promotional offer.
- Penalty APR - Triggered by late payments (60+ days). Can jump to 29.99%. Some issuers apply it to your entire balance, not just new purchases.
- Introductory APR - A temporary promotional rate (often 0%) on purchases or balance transfers. Reverts to the regular APR after the intro period ends.
The Grace Period: Your Free Window
Every credit card has a grace period - typically 21-25 days between your statement closing date and the payment due date. During this window, no interest accrues on new purchases. The catch: you only get the grace period if you paid your previous statement balance in full. If you carried any balance from last month, interest starts accruing on new purchases immediately. This is why carrying even a small balance is costly - it eliminates your grace period on everything.
The Grace Period Trap
If you pay off a $2,000 balance but leave $50 unpaid, you lose the grace period on your entire next month of purchases. Always pay the full statement balance, not just most of it.
How 0% Intro APR Offers Work
Many cards offer 0% APR on purchases or balance transfers for 12-21 months. This can be genuinely valuable for financing a large purchase or paying down existing debt. But read the fine print: after the intro period ends, the regular APR kicks in on any remaining balance. Some cards apply deferred interest - meaning if you do not pay off the full balance by the end of the intro period, you owe all the interest that would have accrued from day one. This is common on store cards but rare on major bank cards.
Real Cost Examples
Scenario: You put $3,000 on a card with 22% APR and make only minimum payments ($60 per month). Time to pay off: 8 years and 3 months. Total interest paid: $2,890. You nearly pay for the purchase twice. Same scenario but you pay $150 per month instead: Time to pay off: 2 years. Total interest paid: $650. Paying $90 more per month saves you $2,240 in interest.
When APR Does Not Matter
- You pay your full balance every month - Zero interest, regardless of APR
- You are comparing rewards cards - Focus on rewards, not APR, if you never carry a balance
- Signup bonus evaluation - The bonus value is separate from the ongoing APR cost
When APR Is Everything
- You plan to carry a balance for any reason - Even one month of carrying changes the math
- You are doing a balance transfer - Compare the intro APR length and the post-intro rate
- Emergency spending - If you might not pay it off immediately, low APR trumps high rewards