Credit Card Interest Calculator

Card issuers charge interest by the day, not the month, and this tool shows that arithmetic. Enter your balance, your APR and the length of the billing cycle and it returns the daily periodic rate, the interest per day and the charge for the whole cycle. The second mode takes a payment as well and splits it into the part that covers interest and the part that actually reduces the balance. It deliberately stops at one cycle rather than projecting a payoff, and it assumes the common method of dividing the APR by 365 against an average daily balance, which is what your statement will name.