Credit Card Interest Calculator

The short answer

• Daily periodic rate = APR ÷ 365. At 22% that is 0.06027% a day.
• A $5,000 balance at 22% costs about $91.21 over a 30-day cycle with daily compounding.
• Pay the full statement balance every month and most cards charge no interest on purchases.
• Paying $200 a month on $5,000 at 22% and spending nothing more still costs about $938 of interest in a year.

Your card's APR

A card’s annual percentage rate is its yearly interest rate. Unlike a loan APR, it does not fold in fees: annual fees, late fees and cash advance fees are charged separately. Most cards have a variable APR, set as the prime rate plus a margin, so it moves when the Federal Reserve changes rates. Your statement lists each APR on the account. For how lenders build fees into a loan’s APR, see our APR calculator.

Average card rates in 2026

"Accounts assessed interest" covers people who carry a balance, so it is the better guide to what a balance costs. Store cards and cards for people with lower credit scores often charge close to 30%.

The daily periodic rate

Cards charge interest by the day. The daily periodic rate is the APR divided by 365 (a few issuers use 360). At 22%, that is 0.22 ÷ 365 = 0.0006027, or 0.06027% a day. On a $5,000 balance that is about $3.01 of interest every day. Over 30 days that adds up to $90.41 before compounding.

The average daily balance

Your balance changes during the month as purchases post and payments arrive. Most issuers use the average daily balance method, including new purchases:

1. Take the balance at the end of each day of the billing cycle.
2. Add them up and divide by the number of days in the cycle.
3. Interest = average daily balance × daily rate × days in the cycle.

With daily compounding, each day’s interest is added to the balance first, so it is included in the average.

A worked example

The new statement balance is $5,396.24: the payment did not even cover the new purchases, so the debt grew. Without the $200 payment, the interest would have been $97.57.

Daily compounding

Compounding adds under a dollar a month on $5,000, but it never stops. A 31-day cycle costs $94.27 on the same balance. The calculator lets you switch compounding and the 360-day year under More options to match your card agreement.

The grace period

Most cards give a grace period on purchases: if you paid the previous statement balance in full by the due date, new purchases are interest-free as long as you pay this statement in full too. Card issuers do not have to offer a grace period, but if they do, the CARD Act rules require the statement to be mailed or delivered at least 21 days before the payment is due.

Losing and regaining the grace period

1. Month 1You pay $1,400 of a $1,500 statement

   The grace period is lost. Interest is charged on the $100 left unpaid and on new purchases from the day they post, but not on the $1,400 you paid in time.

2. Same cycleInterest appears

   With $600 of purchases on day 10 and the $1,400 payment on day 20, about $9.46 on a balance subject to interest averaging $523.42.

3. Month 2 or 3You pay the full statement balance

   Most cards restore the grace period once you pay in full, sometimes after a second month.

Since 2010, issuers may not charge interest on balances from the cycle before last (double-cycle billing), and when you pay part of a balance within the grace period they cannot charge interest on the part you paid on time.

Residual interest

If you carried a balance, then pay the statement in full, you may still see a small interest charge on the next statement. That is residual (or trailing) interest for the days between the statement closing and your payment arriving. Ask the issuer for a payoff amount if you want to clear the card exactly, and pay in full again the next month; the charge should then stop.

When you pay matters

The worked example with the $200 payment made on different days. The earlier a payment arrives, the more days the balance is lower. The saving is small each month, but paying as soon as your paycheck lands, or splitting your payment into two, is an easy habit.

A year of interest

Now add $500 of spending a month to the $200 payment: after a year the interest is $1,662 and the balance has grown to $10,262. Payments that do not cover new spending plus interest only make the debt bigger. To set a payoff date, use our credit card payoff calculator.

What a few points of APR cost

Calling your issuer to ask for a lower rate works more often than people expect, especially with a good payment record. A 0% balance transfer can cut the cost further; see our balance transfer calculator.

Cards with several APRs

One card can have different APRs for purchases, balance transfers and cash advances, plus a promotional rate and a penalty rate. Each part of the balance is charged at its own rate. Under the CARD Act, any payment above the minimum must go first to the balance with the highest APR. Cash advances usually have no grace period, so interest starts the day you take the cash.

Your rights under the CARD Act

• 45 days’ notice before the APR on new purchases goes up or other significant terms change, with the right to refuse and pay off the old balance on the old terms.
• No rate increase in the first year of the account, apart from variable-rate changes, promotional rates ending and late payments.
• A penalty APR can apply to your existing balance only if you are more than 60 days late, and must be reviewed after six months of on-time payments.
• Statements at least 21 days before the due date, and the same due date each month.

Reading your statement

The "Interest Charge Calculation" box lists each balance type, its APR, the balance subject to interest rate (your average daily balance) and the interest charged. Enter those figures here to check them. The minimum payment warning box shows how long paying only the minimum would take, and the payment that clears the balance in three years.

Ways to pay less interest

1. Pay the full statement balance by the due date to keep the grace period.
2. If you carry a balance, stop using that card for new spending.
3. Pay early in the cycle, or make two payments a month.
4. Ask the issuer for a lower APR.
5. Move the balance to a 0% card or a lower-rate personal loan, and clear it during the promotion.
6. With several cards, put extra money on the highest APR first; our debt payoff calculator plans it.

Using the calculator

Enter the balance at the start of the billing cycle, the purchase APR, this cycle’s purchases and payment, and whether you paid last month’s statement in full. Under More options, set the cycle length, the days your purchases post and your payment is credited, daily compounding and the 360- or 365-day year. The results show this cycle’s interest, your balance day by day, how payment timing changes the interest, and a 12-month projection.

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