Guide · Debt
How credit card interest is calculated
Card interest builds every day on your balance. Here is the math in plain English, what the Fed's September 2026 rate hike changes, and the payment that really moves the needle.
By the CalcLedger editorial team · Updated September 2026 · 5 min read · Examples use illustrative rates · How we calculate
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Key takeaways
- Most cards charge interest every day: a daily rate, the APR divided by 365 or 360, applied to your balance.
- On a $6,000 balance at 22% APR, that is about $108 of interest in a 30-day month.
- Pay the full statement balance by the due date and your grace period means no interest on purchases.
- The Fed's quarter-point hike adds only about $15 a year on that balance; paying $250 a month instead of the minimum saves about $7,500.
0.0603%daily rate at 22% APR
≈$108interest in a month on $6,000
$7,527saved paying $250 vs. the minimum
Credit card interest is expensive partly because it is hard to see. Your statement shows an APR, a balance and an interest charge, but not how one becomes the other. The mechanics are standard across most cards, and once you see them it becomes clear which moves save the most.
Step 1: from APR to a daily rate
Your card's APR is a yearly rate, but most issuers charge interest daily. As the CFPB explains, the daily periodic rate "generally can be calculated by dividing the annual percentage rate, or APR, by either 360 or 365, depending on the card issuer." At a 22% APR and a 365-day year, the daily rate is 22% ÷ 365 = about 0.0603%.
Step 2: the average daily balance
Many issuers apply that daily rate to your average daily balance: they add up your balance at the end of each day in the billing cycle and divide by the number of days. The CFPB notes that because "interest is accruing daily, not monthly," paying down part of the balance earlier in the cycle lowers the interest you are charged, if you do not have a grace period.
Example Carry $6,000 at 22% APR for a 30-day cycle: $6,000 × 0.0603% × 30 days ≈ $108 of interest. Pay $2,000 on day 10 and the average daily balance falls to about $4,667, cutting that month's interest to about $84.
Step 3: the grace period
Most cards give you a grace period on purchases: if you pay the full statement balance by the due date, you pay no interest on those purchases. Carry any balance past the due date and you usually lose the grace period, so new purchases start charging interest right away until you pay in full again. Cash advances and most balance transfers typically have no grace period at all.
Tip Paying the full statement balance every month is the only way to pay $0 in card interest. If you can't yet, pay as much as you can as early in the cycle as you can.
What the September 2026 Fed hike changes
Most credit cards have a variable APR set as the prime rate plus a margin. After the Fed raised its target range by a quarter point on September 16, 2026 (Federal Reserve statement of September 16, 2026), the bank prime loan rate rose to 7.00%. Card APRs tied to prime typically rise by the same quarter point within a billing cycle or two, and your issuer must tell you how your variable rate is set in your card agreement.
In dollars, the change is small: on a $6,000 balance, a quarter point adds about $1.25 a month, or about $15 a year. At a fixed $250 payment, payoff takes 33 months instead of 32 and costs about $33 more in interest. The size of your payment matters far more than the Fed.
Why the minimum payment costs so much
Using a common minimum formula, interest plus 1% of the balance with a $35 floor, here is the same $6,000 balance at 22%:
| Monthly payment | Months to pay off | Total interest |
|---|---|---|
| Minimum only (interest + 1%, at least $35) | 215 (about 18 years) | $9,506 |
| Fixed $250 | 32 | $1,979 |
| Fixed $311 | 25 | $1,472 |
| Fixed $400 | 18 | $1,081 |
Total interest on $6,000 at 22% APR
Interest charged monthly, no new purchases
Fixed paymentMinimum payment only
Paying a fixed $250 instead of the minimum saves about $7,527 and about 15 years. Try your own balance in the credit card payoff calculator, which charts both paths.
Watch out Your statement's minimum payment warning shows how long payoff takes at the minimum. Treat it as a warning, not a plan.
Four ways to pay less interest
- Pay a fixed amount above the minimum, and keep paying the same amount as the balance falls.
- Pay early in the cycle or split your payment in two to lower the average daily balance.
- Move the balance to a lower rate with a 0% balance transfer or a fixed-rate personal loan; the balance transfer calculator counts the fee.
- Pick a payoff order if you have several cards: avalanche vs. snowball.
Frequently asked questions
Is credit card interest charged daily or monthly?
Most issuers calculate it daily, using a daily periodic rate on your balance, and add it to your bill once a month.
Why did my interest charge go up if my balance didn't?
A variable APR may have risen after a Fed rate increase, a promotional rate may have ended, or you may have lost your grace period by carrying a balance.
Does paying before the statement date help?
Yes. It lowers your average daily balance, which lowers interest if you are carrying a balance, and it can lower the balance reported to the credit bureaus.
How much does a Fed rate hike raise my card interest?
A quarter-point increase adds about $2.50 a year for every $1,000 of balance you carry. Paying the balance down saves far more.
Sources
- Consumer Financial Protection Bureau: How does my credit card company calculate the amount of interest I owe?
- Consumer Financial Protection Bureau: What is a daily periodic rate on a credit card?
- Board of Governors of the Federal Reserve System: FOMC statement, September 16, 2026
- Federal Reserve Bank of St. Louis (FRED): Bank prime loan rate
Rules, limits and program details are checked against these official sources. Example numbers are calculated by CalcLedger with the formulas on our how we calculate page. Read our editorial policy.
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