Key takeaways
- Card interest is charged daily: your APR ÷ 365, applied to each day’s balance. At 22.99% APR that’s about 0.063% a day.
- Pay the full statement balance by the due date and you usually pay no interest on purchases, thanks to the grace period.
- Paying only the minimum on $6,000 at 22.99% takes 19 years and 7 months and costs $9,638 in interest.
- A fixed payment, a lower rate, or both are what actually shrink the balance.
Credit card interest feels opaque, but the math is simple. It’s also some of the most expensive borrowing most people ever do, which is exactly why it’s worth understanding.
From APR to daily interest
Your card’s APR is an annual rate, but issuers charge interest daily:
- Daily periodic rate = APR ÷ 365. At 22.99%, that’s 0.0630% per day.
- Average daily balance. The issuer adds up your balance at the end of each day in the billing cycle and divides by the number of days.
- Interest for the cycle = average daily balance × daily rate × days in the cycle.
On a $6,000 balance, one month of interest comes to roughly $115. That interest is added to your balance, so next month you pay interest on it too. With daily compounding, a 22.99% APR works out to an effective annual rate of about 25.84%.
The grace period: how to pay zero interest
Most cards give you a grace period of at least 21 days between the end of the billing cycle and the payment due date. If you pay the full statement balance by the due date, new purchases don’t accrue interest at all.
The catch: carry any balance past the due date and you usually lose the grace period. New purchases then start accruing interest from the day you make them, until you’ve paid in full for a full cycle or two. That’s why a card that’s “mostly paid off” can still produce a surprisingly large interest charge.
Cash advances and most balance transfers don’t get a grace period. Interest starts the day of the transaction, often at a higher rate.
Why minimum payments take so long
Minimum payments are usually a small share of the balance (often 1% to 3% plus interest, or a flat floor like $25). As the balance falls, so does the minimum, so the payoff stretches out for years.
Here’s $6,000 at 22.99% APR, with no new charges:
| How you pay | Time to pay off | Total interest |
|---|---|---|
| Minimum only (3% of balance, $25 floor) | 19 years and 7 months | $9,638 |
| Fixed $200 a month | 3 years and 10 months | $3,081 |
| Fixed $300 a month | 2 years and 2 months | $1,674 |
| Paid off in 24 months ($314.21 a month) | 2 years | $1,541 |
The minimum-only path costs more in interest than the original balance. Just freezing the payment at a fixed amount, instead of letting it shrink, cuts years off the payoff. Your statement is required to show how long minimum payments will take, and the payment needed to finish in three years.
How to pay less interest
- Pay more than the minimum, and keep the payment fixed. Set up an automatic payment for a fixed amount so it doesn’t shrink as the balance does.
- Target the highest-rate card first. With several cards, the avalanche method minimizes total interest. The snowball method trades a little interest for quicker wins.
- Ask for a lower rate. Issuers sometimes agree, especially if you’ve paid on time. It costs one phone call.
- Use a 0% balance transfer carefully. A 3% to 5% transfer fee can still beat months of 20%+ interest, if you pay the balance off before the promo ends and stop adding new charges.
- Consider a fixed-rate personal loan. Turning card debt into a fixed payment at a lower rate gives the debt an end date. Compare the payment and total cost in the loan calculator.
- Pay earlier in the cycle. If you carry a balance, paying mid-cycle lowers your average daily balance a little.
Know your rates
Look for these on your statement or cardholder agreement:
- Purchase APR. The rate on everyday spending.
- Balance transfer and cash advance APRs. Often different, sometimes higher.
- Penalty APR. Can apply after a late payment (by law, not before you’re 60 days late for existing balances). It can stay for six months or longer.
- Promotional APR. A temporary rate. Note when it ends.
Most card APRs are variable, tied to the prime rate, so they rise and fall with Federal Reserve rate changes.