Credit Card Interest Calculator (Monthly Cost & Daily Rate)

From APR to a daily number

Card issuers do not charge interest monthly; they charge it daily and add it up at the statement. The APR is divided by 365 to get the daily periodic rate, so 24% becomes 0.0658% a day. That rate is applied to the average daily balance across the cycle, which means a $5,000 balance costs about $3.29 a day. Over a 30-day cycle that is $98.63; a 31-day cycle adds another $3.29. The calculator shows the daily rate and the per-day dollar figure because they make a balance feel expensive in a way an annual percentage never does. Twelve of those cycles add up to the APR, which is why the payoff table uses APR divided by twelve for each month.

The grace period only protects a paid-in-full balance

Interest is not charged on purchases at all as long as you pay the full statement balance by the due date, thanks to the grace period written into most card agreements. Carry even part of the balance and that protection switches off: new purchases typically start accruing from the day they post, and the grace period usually returns only after a full cycle of paying in full. This is why a single month of "just this once" costs more than one month's interest, and why the month-one figure above understates the true price of starting to carry a balance.

$5,000 at 24%: minimum versus fixed

Run the default. Paying only the minimum, defined here as the month's interest plus 1% of the balance with a $25 floor, starts at $150, shrinks every month as the balance falls, and takes about 19 and a half years to reach zero, with roughly $8,900 of interest along the way, more than the original balance. A fixed $250 a month ends the same $5,000 in 26 months for about $1,450 of interest. The gap is not the payment size alone; it is that a minimum recalculated on a falling balance is designed to keep the account open. The minimum payment entry explains the formulas issuers use, and the credit card payoff calculator is the deeper planner for choosing a payment and a date.

Where the per-day figure belongs in a decision

The daily cost is the number to carry around. If $5,000 costs $3.29 a day, a $500 purchase you cannot clear this month costs about 33 cents a day, every day, until it is gone, which reframes "can I afford the payment" as "am I willing to rent this money." It also settles the savings question: interest avoided by paying down a 24% balance beats the yield of any ordinary savings account. And when the balance is large enough that the daily cost is real money, moving it somewhere cheaper for a while can be worth a fee, which our balance transfer guide walks through, catches included.