Credit Card Interest Calculator

See exactly how much interest your credit card charges — per day, per month, and per year. Understand the true cost of carrying a balance.

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Enter your balance and APR to see your interest costs.

Daily Interest
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Every single day this costs you
Monthly Interest
—
~30 days of carrying this balance
Annual Interest (if balance stays same)
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This is the real cost of not paying down your balance

How Credit Card Interest Works

Credit card interest is calculated daily, not annually. Here's the formula:

  1. Daily Rate = APR ÷ 365
    Your 24.99% APR becomes 0.0685% per day.
  2. Daily Interest = Balance × Daily Rate
    A $5,000 balance at 24.99% APR costs about $3.42 per day.
  3. Credit cards typically use the Average Daily Balance method: Your balance is averaged across the billing cycle, multiplied by the daily periodic rate, and applied monthly — interest is usually not compounded daily.

This is why credit card debt can grow quickly — interest is calculated on your average daily balance and added to your account each billing cycle. If you carry a balance month to month, you're paying interest on both your purchases and previously accrued interest.

Use the Payoff Calculator to see a full amortization schedule.