💳 Credit Card Interest Calculator
Find out how much interest accrues on your credit card balance each day and each month.
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How credit card interest accrues
Most credit card issuers charge interest daily on your average daily balance using a daily periodic rate derived from your APR, then total that daily interest across your billing cycle.
The formula
Daily Periodic Rate = APR / 365. Daily Interest = Average Daily Balance × Daily Periodic Rate. Cycle Interest = Daily Interest × Number of Days in the Billing Cycle. If you carried the same balance for a full year, that would total approximately Balance × APR.
This calculator is for general educational purposes. Actual card issuer calculations may use slightly different day counts or compounding methods — check your card’s terms for exact details.
Last reviewed August 2026