Debt Payoff Calculator
Find out how long it takes to become debt-free and how much interest you'll pay. Enter your balance, interest rate, and monthly payment.
At $250.00/month it takes 24 payments. Paying more each month cuts both the time and the interest significantly.
How to use this calculator
Enter your total balance, the interest rate (APR), and the monthly payment you can afford to make. The calculator shows:
- Number of months until the balance reaches zero
- Total interest paid over that period
- Total amount paid (principal + interest)
Try the calculator with your current payment, then increase it by $50 or $100 to see how the payoff timeline responds. On high-rate debt, the relationship is non-linear — a relatively small payment increase can cut months or years from the schedule and save a meaningful amount of interest.
How debt payoff works
On any interest-bearing debt, interest is charged each period on the outstanding balance. When you make a payment, the interest charge for that period is satisfied first, and only the remainder reduces the principal. If the balance is large and the APR is high, a small payment may barely cover the interest — leaving the principal almost unchanged from month to month.
The key insight: every dollar you pay above the interest directly reduces the balance. A smaller balance the following month means a smaller interest charge, which means more of your next payment goes to principal. This positive feedback loop accelerates as the balance falls, which is why the last few months of debt payoff often feel faster than the early months.
This calculator works for any single fixed-rate debt: personal loans, medical bills, car loans, or consolidation loans. For credit card payoff specifically — with its higher typical APRs — see our credit card payoff calculator.
The debt payoff formula
Months to payoff = −log(1 − (r × B) / P) / log(1 + r)
Where B = balance, P = monthly payment, r = monthly rate (APR ÷ 12). Valid only when P is greater than B × r. The calculator simulates each period individually for accuracy.
Worked example — step by step
You have a $5,000 personal loan balance at 18% APR and plan to pay $250/month.
- Monthly rate: 18% ÷ 12 = 1.5%
- Month 1 interest: $5,000 × 1.5% = $75
- Month 1 principal reduction: $250 − $75 = $175
- New balance: $4,825
- Month 2 interest: $4,825 × 1.5% = $72.38. Principal reduction = $177.62. Balance = $4,647.38.
Continuing this way, the debt is paid off in approximately 24 months, with total interest of roughly $975. Now increase the monthly payment to $400:
- Payoff time drops to approximately 14 months
- Total interest falls to approximately $560
- You save roughly $415 in interest and become debt-free 10 months sooner
How to interpret your results
The total interest figure converts your APR into a concrete cost you can compare across options. Seeing that carrying a balance for two years costs nearly $1,000 in interest on a $5,000 debt often motivates more aggressive payoff than the abstract APR percentage alone.
The payoff timeline assumes a fixed balance, fixed rate, and consistent payments with no missed months. Variable-rate debt, new charges to the account, or irregular payments will change your actual payoff date. Re-run the calculator whenever your balance or rate changes significantly.
Avalanche vs. snowball: choosing a strategy for multiple debts
If you have multiple debts, two well-known strategies can guide your payoff order:
- Avalanche: Pay the minimum on all debts, and put every extra dollar toward the highest-APR balance first. Once it's gone, roll that payment to the next-highest rate. This minimizes total interest paid — use this calculator on each debt to compare the savings.
- Snowball: Pay the minimum on all debts, and target the smallest balance first regardless of rate. Early payoff wins provide psychological momentum that can sustain the effort — especially if motivation is a challenge.
Either strategy beats paying minimum payments across the board. The best choice is the one you will actually stick with.
Common mistakes to avoid
- Setting a payment just barely above the minimum. Very small payments result in very slow payoff and high total interest. Use this calculator to find the payment level that gets you debt-free in a time frame you are comfortable with, then commit to that amount.
- Treating all debts identically. High-interest debts cost far more per dollar of balance than low-interest ones. Prioritize by rate (avalanche method) or use this calculator on each debt to quantify exactly what each is costing you.
- Forgetting to account for potential rate changes. Variable-rate loans can reprice. If your rate rises, your monthly interest charge rises with it, and a payment that was making progress may suddenly fall behind. Monitor variable-rate balances actively.
- Not building an emergency fund alongside debt payoff. Without a cash cushion, an unexpected expense forces you back into debt to cover it. A small emergency fund — even $500–$1,000 — breaks this cycle and protects your payoff momentum.
- Closing accounts as soon as they are paid off. Closing a paid-off installment loan can shorten your average credit history and reduce your available credit, potentially affecting your credit score. Weigh this against the benefit of simplifying your financial accounts.
Estimates only. Variable rates, missed payments, or new charges will affect your actual payoff. This is not financial advice.
How we calculate this
The calculator simulates debt payoff month by month. Each period, monthly interest is calculated as balance × (APR ÷ 12). The payment is applied first to interest, then to principal. The loan is considered paid off when the balance reaches zero. If the payment does not exceed monthly interest, the calculator flags the payment as insufficient. Total interest is the sum of all monthly interest charges.
Sources
Frequently asked questions
How long will it take to pay off my debt?
It depends on three things: the balance, the interest rate, and how much you pay each month. Enter those values in the calculator to see the exact number of months and total interest. Even a modest increase in the monthly payment can shave months or years off the timeline.
Why does a low payment never pay off the debt?
If your monthly payment is smaller than or equal to the monthly interest charge, the balance stays flat or grows instead of shrinking. You must pay more than the interest each month to reduce principal at all. The calculator warns you when the payment is too low to make progress.
What is the debt avalanche method?
The avalanche method means paying the minimum on all debts except the one with the highest interest rate — on which you pay as much as possible. Once that balance is cleared, you redirect all freed-up cash to the next-highest-rate debt. This approach minimizes total interest paid and is mathematically optimal.
What is the debt snowball method?
The snowball method means targeting the smallest balance first, regardless of interest rate. Once it's paid off, you roll that payment to the next-smallest balance. This approach pays more total interest than the avalanche method, but the early wins of eliminating accounts can provide strong psychological motivation that helps people stay on track.
Does paying biweekly help with debt payoff?
Yes. Paying half your monthly amount every two weeks produces 26 half-payments per year — equivalent to 13 full monthly payments instead of 12. That extra payment goes directly to principal, shortening the payoff timeline and reducing total interest. It works for any amortizing debt, not just mortgages.
Should I pay off debt or save first?
A common framework is to first build a small emergency fund (often one to three months of essential expenses), then aggressively pay off high-interest debt, then resume building savings and investing. The logic: high-rate debt costs more in interest than most savings earn, making debt payoff a guaranteed risk-free return equal to the interest rate.
What if my interest rate is variable?
This calculator assumes a fixed interest rate. On variable-rate debt, the rate and therefore the payoff timeline can change over time. If you have variable-rate debt, use the calculator with a realistic estimate of your current rate, and re-run it if the rate changes significantly.
Does this calculator work for multiple debts at once?
This calculator handles a single debt at a time. For a clean projection, run each debt separately to understand its individual payoff timeline and interest cost. If you want to model the combined payoff of multiple debts in priority order, a dedicated multi-debt payoff tool is more appropriate.