Debt Payoff Calculator
Find out how long it takes to become debt-free and how much interest you pay with your monthly payment.
Debt Payoff Calculator — input your values
What does this financial calculator do?
The debt payoff calculator shows exactly how long it takes to clear a debt when you pay a fixed amount every month. It applies the annual rate monthly to the remaining balance, then subtracts your payment, month by month, until the debt reaches zero.
The results include the total interest paid, the total amount repaid, a monthly schedule and a declining balance chart. Add an extra payment to see how much sooner — and how much cheaper — you can become debt-free.
Formula and variables
Each payment covers the accrued interest first; whatever remains reduces the principal.
| Symbol | Meaning |
|---|---|
| r | Monthly interest rate (annual rate ÷ 12) |
| payment | Fixed monthly payment (plus any extra) |
| balanceₜ | Remaining debt after month t |
Worked example
A $10,000 debt at 18% APR with a $300 monthly payment.
- Monthly rate: 18% ÷ 12 = 1.5%.
- First month's interest: 1.5% × $10,000 = $150.
- First month's principal paid: $300 − $150 = $150.
- The balance falls slowly at first and faster later — fully paid in ≈ 48 months.
- Total interest ≈ $3,533; total paid ≈ $13,533.
Answer: Debt-free in about 4 years, paying roughly $3,533 in interest.
Tips and common mistakes
Tips
- The avalanche method — paying extra on the highest-APR debt first — minimizes total interest.
- The snowball method — paying extra on the smallest balance first — builds momentum and motivation.
- Every extra dollar paid early prevents interest forever; pay extras in the first months if you can.
- Refinancing to a lower rate helps, but only if the fees are small and the payment stays disciplined.
Common mistakes to avoid
- Making only interest-covering payments and never shrinking the principal.
- Taking on new debt while paying off old debt, which keeps the total balance flat.
- Dropping the payment when the balance feels small — the final stretch is where compounding loses its power.
Debt Payoff Calculator — frequently asked questions
How long does it take to pay off debt?
Divide the balance by your monthly payment to get a rough idea, then account for interest: at 18% APR, $10,000 with $300 monthly payments takes about 4 years and adds roughly $3,500 in interest.
What is the difference between the snowball and avalanche methods?
Avalanche pays extra toward the highest-APR debt first, minimizing total interest. Snowball pays extra toward the smallest balance first, producing quick wins. Both work; pick the one you will stick with.
How does interest compound on debts?
Most debts charge interest monthly on the outstanding balance. If your payment is below the monthly interest, the balance grows instead of shrinking — which is how balances spiral.
Should I pay off debt or save first?
Keep a small emergency fund, then attack high-interest debt: paying 18% interest is the same as earning an 18% guaranteed return, which no savings account matches.
What if I have multiple debts?
Enter the total balance and a weighted-average APR, or model each debt separately. The results are most useful when payments are consistent each month.
How can I pay off debt faster?
Raise the payment amount, reduce the rate (balance transfer or refinance), avoid new charges, and apply windfalls like tax refunds straight to the principal.