Credit Card Interest Calculator
See how much interest your card charges this billing cycle, worked out the way banks do it: your average daily balance × the daily rate × the days.
With a grace period, purchases usually carry no interest. Cash advances usually have no grace period: check your card terms.
Payments and refunds go to the higher-rate balance first (the US rule for amounts above the minimum; many other banks do the same). A transaction counts from its own day to the end of the cycle.
Balance day by day
| Days | Count | Balance | Day-total |
|---|
If you only pay the minimum
Starting from the new statement balance, with no new spending, at this rate.
How your interest is worked out
Average daily balance × daily rate × days in the cycle.
- 1
Daily rate
24% ÷ 365= 0.06575% a day
- 2
Average daily balance
Sum $60,000÷ 30 days= $2,000.00
- 3
Interest this cycle
$2,000.00 × 0.06575%× 30 days= $39.45
- 4
Your new balance
$2,000.00 owed+ $39.45 interest= $2,039.45Minimum due: $61.18
Read more: the formula, worked examples, grace periods and cash advances
Card interest is charged on the balance you carry each day, not just the figure on your statement. Every purchase, payment and cash advance changes the balance from that day on, so when you spend and pay inside the cycle matters.
The formula
daily rate = APR ÷ 365 (or ÷ 360)
average daily balance = (balance at the end of each day, added up) ÷ days in the cycle
interest = average daily balance × daily rate × days in the cycle
new balance = balance after payments and spending + interest
quick estimate = average daily balance × APR ÷ 12
effective yearly rate = (1 + APR ÷ 365)^365 − 1
Worked example
You start the cycle owing $2,000 at 24% APR, with a 30-day cycle and no new spending or payments. The daily rate is 24 ÷ 365 = 0.06575% a day. The balance is $2,000 every day, so the day-total is $2,000 × 30 = $60,000 and the average daily balance is $60,000 ÷ 30 = $2,000. Interest is $2,000 × 0.24 ÷ 365 × 30 = $39.45 (about $1.32 a day), and the new balance is $2,039.45.
The APR ÷ 12 shortcut gives $2,000 × 0.24 ÷ 12 = $40.00. A bank using a 360-day year charges $2,000 × 0.24 ÷ 360 × 30 = $40.00, and adding the interest every day (compounding) makes it $2,000 × ((1 + 0.24 ÷ 365)^30 − 1) = $39.83. With daily compounding all year, 24% APR works out at (1 + 0.24 ÷ 365)^365 − 1 = 27.11% a year.
A minimum of 3% of the balance (at least $25) is 3% × $2,039.45 = $61.18. Paying only the minimum from there, with no new spending, costs $461.92 of interest in the next 12 months: you pay $706.73 and still owe $1,794.64. It takes 140 months to clear, with $2,827.95 of interest in all.
Example with transactions
Same $2,000 at 24%, 30 days, with a $450 purchase on day 8, a $600 payment on day 15 and a $200 cash advance on day 22 at 29% with a 5% fee ($10).
| Days | Count | Purchases | Cash |
|---|---|---|---|
| 1–7 | 7 | $2,000 | $0 |
| 8–14 | 7 | $2,450 | $0 |
| 15–21 | 7 | $1,850 | $0 |
| 22–30 | 9 | $1,850 | $210 |
Purchases: 7 × $2,000 + 7 × $2,450 + 16 × $1,850 = $60,750, so the average daily balance is $60,750 ÷ 30 = $2,025 and the interest is $60,750 × 0.24 ÷ 365 = $39.95. Cash: 9 × $210 = $1,890, an average of $63, and $1,890 × 0.29 ÷ 365 = $1.50. Total interest is $41.45 and the new balance is $1,850 + $210 + $41.45 = $2,101.45. If you had paid the last statement in full (grace period), only the $1.50 on the cash advance would be charged.
Grace periods and cash advances
Most cards give a grace period of 21–25 days or more between the statement date and the due date. If you pay the whole statement balance by then, new purchases carry no interest. Once you carry a balance, interest usually runs on new purchases from the day you make them until you have paid in full again. Cash advances, and often balance transfers, usually have no grace period and a higher APR, and many cards add a cash advance fee. Your card terms say exactly how yours works.
Payment order
US: since the CARD Act of 2009, amounts above the minimum must go to the highest-rate balance first. Many banks elsewhere do the same, but not all: some put payments toward the lowest-rate balance first. This calculator sends payments to the higher-rate balance first.
Assumes balances are end-of-day amounts, a transaction counts from its own day, any credit balance earns nothing, and interest is added at the end of the cycle unless you pick daily compounding. Some banks round the daily rate or the interest, so your statement may differ by a few cents. Checked on 13 October 2026.
Common questions
How is credit card interest calculated?
Most cards use the average daily balance. The daily rate is the APR ÷ 365. Add up the balance at the end of each day in the billing cycle, divide by the number of days to get the average daily balance, then multiply by the daily rate and the days. $2,000 for a 30-day cycle at 24% APR costs $2,000 × 0.24 ÷ 365 × 30 = $39.45.
What is the daily periodic rate?
It is your APR divided by the days in a year, usually 365 (some banks use 360). At 24% APR it is 24 ÷ 365 = 0.06575% a day, so each $1,000 you carry costs about 66 cents a day.
Do I pay interest if I pay my statement in full?
Usually not on purchases. Most cards give a grace period: if you pay the full statement balance by the due date, new purchases carry no interest. Cash advances usually have no grace period and start charging interest the day you take them, often at a higher APR, so check your card terms.
Why is my interest different from APR ÷ 12?
APR ÷ 12 is a quick estimate. Real statements use a daily rate and the actual days in the cycle, and your balance changes as you spend and pay. On $2,000 at 24%, APR ÷ 12 gives $40.00, while a 30-day cycle gives $39.45 and a 31-day cycle $40.77.
What is the effective annual rate on a credit card?
When interest is added to the balance every day, you pay interest on interest, so the true yearly cost is a little above the APR. At 24% APR it is (1 + 0.24 ÷ 365)^365 − 1 = 27.11% a year.
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