What Is a Revolving Debt Cost Calculator?

A revolving debt cost calculator totals what a credit card or line-of-credit balance costs when you repay it the way the issuer designed — with a minimum payment that is a percentage of the balance. Unlike an installment loan, which fixes both the payment and the payoff date, a revolving account recalculates the minimum every month as the balance falls, so the repayment schedule quietly stretches and there is no built-in end date at all.

The cost difference is dramatic. A balance repaid at the minimum can run for years longer than the same balance repaid at a fixed amount, and the interest bill can approach or exceed the original principal. This calculator models the true percentage-based schedule — including the payment floor that issuers apply and the shifting split between interest and principal — so the price of minimum payments is visible as a number rather than a feeling.

How It Works

Each month the calculator charges interest on the outstanding balance at the monthly rate, which is the APR divided by twelve. The payment is the greater of the minimum payment percentage multiplied by the balance, or the fixed floor the issuer enforces, plus any extra you add. The payment covers interest first and principal second, and the process repeats until the balance reaches zero.

Because the payment is recalculated from the falling balance each month, the schedule is not a simple amortisation: early payments are large and mostly interest, while later payments shrink toward the floor. The calculator records the first and final payments so that drift is visible, and it runs the schedule a second time with the extra monthly payment included, in order to report the interest saved and the months removed from the payoff.

Understanding Your Results

The primary card reports total interest with the cost per $100 of balance beneath it. The three-stat bar gives the months to payoff, the first payment, and the total paid, while the breakdown table splits the total into principal and interest with each share, making the interest share impossible to miss on a high-rate revolving balance.

Summary Statistics adds the payoff date, the final payment, the interest and months saved by paying extra, and the monthly interest rate for comparison with the payment rate. The comparison between the two rates is the clearest way to see the trap: when a card charges 1.83% a month in interest and the minimum requires only 2.5% of the balance, barely a fifth of every payment touches the principal, and the schedule lengthens with every month you stay on it. Treat the output as a planning estimate: issuers change floors and formulas, promotional rates expire, and new spending on the account restarts the clock. The single most effective change is to stop using the percentage minimum as your payment — set a fixed amount above it, keep it there, and the schedule regains the fixed end date that installment loans have by design. Pay attention to the first payment figure as well: it is the closest the schedule ever gets to a fixed payment, and matching it deliberately every month turns the revolving line into something that behaves like the installment loan it never was.