Credit card interest calculator

For a flat $3,000 balance carried all 30 days at 26.99% APR (365-day year), interest for that one billing cycle is about $66.55. That assumes one balance for the whole period—not purchases and payments on different days.

Load the $3,000 · 26.99% preset above or enter your own balance, APR, and cycle length.

For one billing cycle, issuers usually apply a daily periodic rate to the balance they charge interest on, then multiply by days in the cycle. In symbols: Interest ≈ Balance × (APR ÷ 100) ÷ day basis × days, where balance may be your statement amount or average daily balance (ADB).

Use Quick estimate for a statement balance, or Average daily balance to enter daily purchases and payments—the calculator shows each step.

For one statement cycle only: if you carried $10,000 every day at 22% APR for 30 days (365-day year), interest would be about $180.82. Real bills change when you pay down the balance or when purchases post on different days.

Enter your balance, APR, and days in the calculator—or use ledger mode if activity varies through the cycle.

A 20% purchase APR is in the range many US cardholders see—plenty of accounts advertise higher rates, and store cards or penalty APRs can be much higher. Lower APRs often go to strong credit profiles.

Compare your APR to your statement and use the calculator to see dollar interest for one cycle—for example, $1,000 at 20% for 30 days is about $16.44 with a 365-day year.

When your card offers a grace period on purchases and you pay the statement balance in full by the due date, you typically do not pay purchase interest on those purchases for that cycle. The CFPB describes how grace periods work.

Carrying a balance usually ends the grace period for new purchases until you pay in full again. Cash advances often have no grace period—check your card agreement.

ADB is the sum of each day’s end-of-day balance in the cycle divided by the number of days. Example: $100 all month → ADB $100; a $45 purchase on day 11 only → ADB $130 on a 30-day cycle.

Use Average daily balance mode to enter daily purchases and payments—the calculator computes ADB before interest.

On many statements, interest charged and finance charge are the same line-item cost for carrying a balance that cycle. “Finance charge” can also include certain fees, depending on the account.

This calculator focuses on card interest and includes an ADB activity ledger. Our finance charge calculator uses the same math with finance-charge wording and custom day counts.

Pay the statement balance in full by the due date when your card offers a grace period on purchases. If you carry a balance, paying more than the minimum and paying before the due date lowers the balance your issuer charges interest on.

This calculator shows the cost of one cycle with a balance—pair it with our debt payoff calculator when you want a multi-month plan.

Usually no. The minimum payment keeps the account in good standing, but the remaining balance typically keeps accruing interest in the next billing cycle (unless a promotion applies).

Estimate one cycle here; model extra payments and payoff dates with our debt payoff calculator.

Yes. This credit card interest calculator answers: “How much interest for this statement cycle?” A payoff calculator answers: “How long until I’m debt-free?” with ongoing payments across months or multiple cards.

Use this page for one-cycle math; use the debt payoff calculator for a payoff timeline.

Most cycles run 28–31 days, depending on the month and your issuer’s calendar. When people ask about monthly card interest, they usually mean one statement period, not a calendar month—use the days in billing cycle line on your statement when it’s listed.

The calculator supports 28, 29, 30, and 31 days in Quick estimate and Average daily balance modes.

Enter the purchase APR for everyday charges—the rate shown in your Schumer box or statement for purchases. Cash-advance and penalty APRs are separate; this calculator models one APR on one balance for illustration.

In Quick estimate, open Advanced to choose a 365 or 360 day-count year when your class or disclosure specifies it.

Many cards compound interest daily as your balance changes. This tool uses the standard one-cycle estimate: balance (or ADB) × daily periodic rate × days. That matches many homework and budgeting examples but may differ slightly from your issuer’s rounding or balance method.

Treat your statement’s interest charged line as the source of truth for what you actually owe.

Yes. Use Export CSV or Export PDF for inputs, interest totals, daily rate, and a short summary—no account required.

In Average daily balance mode, CSV can also include a table of daily purchases, payments, and end-of-day balances for the cycle.

Yes. No account or signup—presets, average daily balance ledger, step breakdown, optional daily table, and CSV/PDF export run in your browser.

No. This is illustrative math for learning and planning—not a recommendation to borrow, pay, or invest.

Confirm rates, fees, and interest lines on your statement and talk with qualified professionals before major credit decisions.

Simple interest (I = Prt) fits flat principal over time in years. Card interest for one cycle uses a daily rate on a balance for a statement period.

See our simple interest calculator for homework-style problems.