Credit Card Interest Calculator - Estimate Card Charges

The credit card interest calculator estimates finance charges with simple interest: balance × APR / 100 × months / 12. A $5,000 balance at 18% APR carried for 12 months costs $900 under that formula, and the same balance for six months costs $450. The method is useful when you want a fast, transparent cost of carrying a balance without building a full amortization schedule. It answers planning questions such as how much a delayed payoff costs, whether a promotional APR is worth a transfer fee, and how a rate hike would change the annual carrying cost. Issuers typically apply a daily periodic rate equal to APR / 365 (or 360) to an average daily balance, and they add new purchases, payments, and fees during the cycle. Simple interest ignores those intra-month changes and assumes the starting balance stays outstanding for the whole period. That makes the estimate a ceiling if you pay the balance down, and an understatement if you add new charges. The credit card interest calculator also does not model grace periods. If you pay the statement in full by the due date and the account has a grace period, purchase interest may be zero even though APR is not. Use cases include budgeting a carry cost before a large purchase, comparing two cards' APRs on the same balance, and showing why a 22% card is more expensive than a 15% card even before compounding. Change months to see a one-cycle cost versus a one-year cost. Recalculate after a payment or a promotional-rate expiry. Caveats: cash advances and balance transfers often use different APRs and may have no grace period. Penalty APRs, late fees, and interest on interest are outside this formula. Confirm the periodic rate and balance method on your card agreement. For a declining balance with a fixed payment, use a payoff calculator instead of this simple-interest estimate. Used as a planning check, the credit card interest calculator makes borrowing cost easier to compare.