How credit card interest is calculated

The balance, rate and days determine the charge

Many U.S. credit-card companies calculate interest daily. For one unchanged APR, you can multiply the interest-bearing average daily balance by the daily rate and the number of days in the billing cycle. CFPB: how issuers calculate interest.

Cycle interest = average daily balance × (APR ÷ 100 ÷ annual divisor) × cycle days

First check whether the balance bears interest. Qualifying purchases with an active grace period can avoid purchase interest when you meet the full-payment conditions. The calculation below assumes interest is already accruing. CFPB: purchase grace periods.

What APR means—and how it becomes a daily rate

Credit cards charge interest for borrowing money from the issuer. The interest rate sets that borrowing cost; paying the required minimum on time can still leave a balance accruing interest. Qualifying purchases can avoid the charge under the account's grace-period conditions. CFPB: interest as the cost of borrowing.

APR expresses a periodic interest rate annually. For the corresponding APR disclosed on a credit card, Regulation Z annualizes the periodic rate: a 2% monthly rate corresponds to 24% APR. The dollar charge still depends on the balance and time. Regulation Z §1026.14(b) and comment 14(b)-1.

A daily periodic rate commonly uses APR divided by 360 or 365, according to the account terms. At 24% APR on a 365-day basis, the daily rate is 0.0657534…%, or 0.000657534… as a decimal multiplier. Multiply dollars by the decimal. CFPB: daily periodic rates.

Converting APR does not explain why an issuer offered that rate. Application and credit information can affect pricing; a variable APR can also change with its reference index. Read your disclosed rate rather than inferring it from the balance. CFPB: offered rates · CFPB: fixed and variable APRs.

How much interest do credit cards charge?

Your dollar charge depends on your APR, interest-bearing balance and days. For a U.S. market benchmark, the Federal Reserve's October 7, 2026 release reports these commercial-bank credit-card figures for August 2026. Federal Reserve G.19: Terms of Credit and footnote 5.

The two measures describe different populations and calculations. Neither determines your APR or means every purchase incurs interest. Use your statement's disclosed rate in the cycle calculator; the 18%, 24% and 30% examples show how a rate becomes a dollar charge.

Calculate a cycle in four steps

1. Separate the balances. Use the purchase APR for purchases and the relevant rate for each other category.
2. Find the daily rate. Convert APR to a decimal and divide by the annual basis in the agreement.
3. Determine the balance used each day. Apply the account's rules for transactions, payments, credits, fees and accrued interest.
4. Add the daily charges. With one fixed rate, the sum equals average daily balance × daily rate × cycle days.

The U.S. Bank calculation guide describes the average-balance method. Use the actual cycle length: with a $1,000 average balance and 24% APR on a 365-day basis, 28 days gives $18.41, 30 gives $19.73 and 31 gives $20.38. APR divided by 12 would instead give $20—a monthly approximation.

Keep the full rate and balances through the calculation, then round the result. An issuer's minimum-interest charge or rounding rules may still change its billed amount. A leap year does not automatically replace a contractual 365-day divisor with 366.

Your closing balance is not your average daily balance

Suppose the interest-bearing balance is $1,000 for ten days, then a $300 payment reduces it to $700 for the next twenty days. This simplified example keeps accrued interest separate and includes no other entries.

Average daily balance = $24,000 ÷ 30 = $800
Cycle interest = $800 × (0.24 ÷ 365) × 30 = $15.78

The average is $800, although the final principal balance is $700. Averaging just the first and last balances would give $850 and miss how long each balance lasted. Two accounts can finish at the same balance and still have different interest charges.

In the calculator, choose “A starting balance and a payment date,” enter a $1,000 balance and $300 payment on day 11, and keep daily interest separate. The day-by-day table shows how the $800 average is formed.

When accrued interest enters the next day's balance

Daily calculation and compounding describe different parts of the method. Compounding occurs when earlier interest becomes part of a later interest-bearing balance. The reviewed Chase agreement includes prior-day interest in its daily balance and divides APR by 365. That establishes the method for that agreement, not every card. Chase cardmember agreement, PDF page 17: Interest Charges.

Our example starts with $1,000 at 24% APR on a 365-day basis. With no payments, no new transactions and daily compounding for 30 days:

Interest = $1,000 × [(1 + 0.24 ÷ 365)³⁰ − 1] = $19.92

The $19.92 differs from the $19.73 result for an average daily balance of exactly $1,000. Here the balance starts at $1,000 and grows each day; its average is higher. If a statement's average already incorporates accrued interest, applying another compounding factor would count the effect twice.

To reproduce this example, choose the starting-balance method, enter a $0 payment and select “Add prior-day interest to the next balance.” The annual APR remains 24%; an effective compounded annual growth calculation would answer a different question.

What changes when the same payment posts earlier

A payment can reduce an interest-bearing balance for more days when it posts earlier. The CFPB explains this relationship for daily interest. CFPB: how payments affect interest.

Use the two posting-day fields to hold the payment amount constant and compare the same cycle. Changing the compounding setting changes both scenarios together. This comparison does not determine a due date, guarantee payment-posting speed or recommend a payment you can afford.

Why paying on time can still leave interest

Making the minimum payment by the due date and meeting the conditions for avoiding purchase interest are different requirements. A minimum payment can leave most of the debt outstanding. See the minimum-payment examples below. Capital One: minimum payments.

With an active purchase grace period, qualifying purchases can avoid interest when the required balance is paid in full by the due date. Carrying a balance can remove that protection, including for new purchases. Cash advances generally start accruing from the transaction date. CFPB: full payment and lost grace.

A grace period runs from cycle closing to the due date. Purchases early and late in the same cycle can share that deadline, so each purchase does not receive the same number of interest-free days. The statement-delivery requirement of at least 21 days before payment is due is not a promise that every transaction has a grace period.

How is the minimum credit-card payment calculated?

The issuer's agreement defines the calculation. In the reviewed Chase agreement, add past-due amounts and required financing-plan payments to the larger of a $40 floor (or the total owed if smaller) and 1% of the eligible new balance plus billed periodic interest and late fees. Certain financing-plan balances are excluded from that 1% calculation. Chase agreement, PDF page 1: Minimum Payment.

Simplified examples for that agreement: assume no past-due amounts, late fees or financing-plan obligations. The new balance below is the statement balance used in the formula, including its billed interest; do not add that interest again when identifying the balance.

Use the minimum printed on your statement. Paying it meets a different goal from paying the full balance or clearing debt by a chosen date. The payoff estimator models a payment you choose; it does not determine your issuer's required minimum.

Calculate different APR categories separately

A statement can show purchases, transfers and cash advances at different rates. It must identify each different APR category and the balance in it. CFPB: balances with different APRs.

For our example, a $1,000 interest-bearing average balance at 18% plus another $1,000 at 24%, over 30 days using 365, gives $14.794520… + $19.726027… = $34.52 before any account-specific rounding adjustments. A combined $2,000 closing balance cannot reveal those inputs.

Amounts above the minimum generally go to the highest-rate balance first; issuers generally choose how the minimum portion is allocated. Deferred-interest plans have additional rules. The cycle calculator models one APR and one payment to that modeled balance, so it cannot reconstruct payment allocation across an entire mixed-rate account.

A 0% transfer, purchase promotion and deferred-interest offer differ

A 0% balance-transfer offer does not necessarily make new purchases interest-free. Carrying the transferred balance can affect purchase grace, even while the transfer itself bears no interest. Check whether the offer separately covers purchases. CFPB: purchases after a low-rate transfer.

“No interest if paid in full” is conditional deferred interest. If its payoff condition is missed, interest can reach back to the purchase date. Minimum payments may not clear the promotional balance by the deadline. CFPB: deferred-interest plans.

A fixed 0% entry in the calculator models zero interest for the selected period; it does not model deferred charges or a later rate change.

How long do introductory APR periods last?

The duration belongs to the specific offer. Wells Fargo describes 6–21 months for introductory balance-transfer offers in its educational guide. That is an issuer's illustrative range, not a measured market average or a universal maximum. Wells Fargo: how balance-transfer cards work.

Months, billing cycles and transfer deadlines measure different things. A deadline for making a qualifying transfer does not restart a promotion measured from account opening. Check the stated end date, eligible transactions, transfer fee and APR that follows.

The card product and particular promotion determine the advertised term. Wells Fargo also states that offers can vary over time and by marketing channel. These examples do not establish a rule that a higher credit score automatically buys more promotional months; use the offer disclosed to you.

The CFPB explains that an introductory rate must last at least six months unless a payment is more than 60 days late. A variable introductory rate can still change with its reference index during that period. This protection does not establish a typical offer length. CFPB: introductory-rate duration and exceptions.

Why interest can appear after you pay the statement balance

For a balance already accruing interest, charges generally continue until the issuer receives payment. Paying the amount printed on a statement can leave interest from the days after that statement closed. CFPB: interest while a carried balance is being paid off.

In our simplified example, $1,000 remains interest-bearing for ten more days at 24% APR on a 365-day basis. With no compounding or other entries, the additional interest is $1,000 × 0.24 ÷ 365 × 10 = $6.58. That amount was not part of the earlier $1,000 statement snapshot.

To settle an interest-bearing account completely, obtain the issuer's current payoff amount through its official channel and check subsequent charges. An app's current balance and the statement balance describe different snapshots; neither automatically represents the average daily balance. See statement balance versus current balance.

What to check when your statement differs

• The cycle's start and closing dates, and actual number of days.
• Each APR and its “balance subject to interest” category.
• The contractual annual divisor and daily-balance method.
• Whether earlier interest enters the next day's balance.
• Transaction, payment and credit posting dates.
• Purchase-grace status, promotions, fees and minimum-interest charges.
• The account's rate and charge rounding, including adjustments.

Public agreement examples can help explain a method, but your account may have different terms. Ask your issuer for your agreement; the CFPB agreement database also explains how to find it.

Can the interest charge reveal the APR?

Only approximately, with enough information. If one constant rate applies and fees and adjustments are excluded, rearranging the formula gives: APR (%) = interest × annual divisor × 100 ÷ (average daily balance × cycle days). A rounded $19.73 charge on a $1,000 average over 30 days using 365 implies about 24.0048%, consistent with 24% after cent rounding. That is not proof of a rate accurate to four decimal places.

The disclosed APR is the better starting point. For longer-term planning, the monthly payoff estimator uses a separate approximation and provides a payment schedule.

Sources and calculation notes

The linked passages were checked on October 10, 2026. They establish general U.S. guidance, the identified issuer's method, or the dated statistics and offer terms labeled above. Our ledgers and worked dollar amounts are hypothetical calculations, not quotations of customer charges.

1. [1]CFPB: how issuers calculate interest — daily balances, rate categories and payments.
2. [2]CFPB: purchase grace periods — full-payment conditions, lost grace and statement timing.
3. [3]Regulation Z §1026.14(b) — corresponding APR and official comment 14(b)-1.
4. [4]CFPB: finding a card agreement — public examples and account-specific terms.
5. CFPB: daily periodic rates — annual divisor and daily interest.
6. U.S. Bank: interest calculation — average daily balance × daily rate × days.
7. Chase agreement, PDF page 17 — daily balance including prior-day interest; 365 divisor.
8. CFPB: interest after a carried balance is paid — accrual until receipt of payment.
9. CFPB: different APR categories — disclosed balances and payment allocation.
10. CFPB: purchase interest with a promotional transfer.
11. CFPB: deferred-interest offers — payoff deadlines and retroactive interest.
12. CFPB: offered interest rates · CFPB: variable APR.
13. Capital One: minimum-payment explanations — issuer formulas and paying only the minimum.