Credit Card Interest Calculator

Estimate monthly interest charges based on balance and APR.

Card balance APR (%)

Result
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How this calculation works

What each input means

Card balance — Balance interest accrues on for the month.
APR (%) — Nominal annual rate; converted to monthly periodic rate r = APR ÷ 100 ÷ 12.

Formula used

Estimated monthly interest ≈ balance × r (simple interest on the current balance; not minimum-payment schedules).

Real cards use daily balance methods, grace periods, and promo rates—confirm with your issuer.

How this result is estimated

This credit card calculator applies the formulas described on this page to the values you enter. Outputs are not financial, tax, legal, or medical advice.

Inputs are user-provided and may include rounding.
Where accuracy, eligibility, or obligations matter, rely on official disclosures and licensed professionals.

Last reviewed: 2026-04-17

Frequently asked questions

Is this calculator result exact?

It is an estimate based on your inputs and may differ from official or provider-specific calculations.

Does this site provide financial, tax, or legal advice?

No. Each tool applies explicit formulas to values you supply. Financial, tax, and legal conclusions belong with licensed professionals and official documents.

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