How the payoff is simulated
This calculator does not use a single formula; it walks through your debt one month at a time. Each month it adds the interest owed on the current balance, subtracts your fixed payment, and carries the new, smaller balance into the next month. It repeats until the balance reaches zero, then reports how many months that took and how much interest piled up along the way.
Because interest is charged on whatever is still owed, the early months are interest-heavy and the balance falls slowly. As the principal shrinks, less of each payment is eaten by interest and the debt clears faster — which is why progress feels like it accelerates near the end.
Making sense of the results
The months-to-payoff figure is the headline: how long the debt lasts at your current payment. The total interest is the extra you hand over on top of the amount you owed.
The balance chart shows the debt falling toward zero over time, and the donut chart contrasts the original balance with the interest you pay to clear it.
Paying off faster
Small changes have an outsized effect on a debt:
- Increasing the monthly payment cuts both the timeline and the total interest sharply, because less interest accrues each month.
- Making one extra payment a year, or rounding the payment up, quietly shortens the schedule.
- Lowering the rate — through a balance transfer or consolidation — frees more of each payment to attack the principal.
A note on real debts
This assumes a single balance, a fixed rate and a constant payment with no new charges. Real revolving debt can change if you keep spending or if the rate is variable. Use this as a planning guide and avoid adding new balances while you pay it down.
Formula
each month: interest = balance·annualRate/1200; balance += interest − paymentFrequently asked questions
- What if my payment is too small?
- If the payment is less than the first month’s interest, the balance grows and the debt is never repaid. Increase your payment.