How credit card interest works
Pay your statement balance in full by the due date and you generally pay no interest on purchases. Carry a balance and interest adds up fast.
Sourced from official pages · Updated September 30, 2026💡 Key takeaways
- A card’s APR is a yearly rate usually applied as a daily rate on your balance.
- Pay the full statement balance by the due date and you generally pay no interest on new purchases (the grace period).
- Paying only the minimum can take years and cost a lot in interest.
- Your statement must be delivered at least 21 days before the payment due date.
APR and daily interest
A card’s purchase APR is a yearly rate. Issuers typically apply it as a daily rate to your balance. Most cards have a variable APR that moves with a benchmark rate.
The grace period
If you pay the full statement balance by the due date each month, you generally are not charged interest on new purchases. If you carry a balance, you usually lose the grace period and interest accrues on new purchases from the transaction date. By law your issuer must deliver your statement at least 21 days before the payment due date.
Minimum payments
Paying only the minimum keeps the account current but can take years to repay and cost a lot in interest. Your statement includes a warning that shows how long it would take to pay off the balance with minimum payments.
Balance transfers
Some cards offer a 0% intro APR on balance transfers for a limited time, usually with a transfer fee (often a percentage of the amount). Compare the fee with the interest you would save, and plan to repay before the promotion ends.
How interest is calculated
Most issuers divide the APR by 365 to get a daily rate and apply it to your balance each day, then add the interest at the end of the billing cycle. Different balance methods exist; your card agreement explains which applies.
Ways to pay less interest
- Pay the statement balance in full each month.
- If you carry a balance, pay as much as possible above the minimum.
- Consider a 0% intro APR balance transfer if the fee is lower than the interest you would save.
- Ask your issuer about a lower APR if your credit has improved.
🔤 Key terms
| Term | Meaning |
|---|---|
| APR | Yearly interest rate |
| Daily periodic rate | APR divided by 365 |
| Grace period | Time to pay without interest on new purchases if you paid in full |
| Statement balance | The balance at the end of the billing cycle |
| Minimum payment | The smallest amount to keep the account current |
Scenarios
| Situation | What happens |
|---|---|
| You pay the statement balance in full | You generally pay no interest on new purchases |
| You pay less than the full balance | Interest accrues on the balance and new purchases |
| You pay only the minimum | The balance falls slowly and interest builds |
🧮 Worked example: $5,000 at 20% APR paying $150 a month
With a $5,000 balance, a 20% APR and a fixed $150 payment, it takes about 4 years and 2 months to reach zero, and total interest is roughly $2,359. Paying the minimum only would take longer. Try it in the credit card payoff calculator. Illustration only.
⚠️ Common mistakes to avoid
- Paying only the minimum every month.
- Assuming the grace period applies when you carry a balance.
- Missing the due date, which can trigger a late fee.
- Ignoring that a variable APR can change.
🛠️ Try it yourself
❓ Frequently asked questions
What is a grace period?
The time between the end of a billing cycle and the due date when you can pay without interest on new purchases, if you paid the previous balance in full.
Is a 0% intro APR really free?
Often there is a balance transfer fee, and the regular APR applies after the promotion.
Can my APR change?
Most cards have variable APRs; issuers must generally give notice before certain increases.
Does interest compound?
Interest is typically added to the balance so you can pay interest on interest; see your agreement.
📚 Sources
This guide is general information, not financial, tax or legal advice. Rules and limits change; confirm with the sources above or a licensed professional.