Debt Payoff Calculator
Free debt payoff calculator comparing the snowball and avalanche methods side by side, with payoff dates, total interest, and CSV export.
How the debt payoff calculator works
List your debts — balance, interest rate, and minimum payment for each — add whatever extra you can put toward debt each month, and this calculator simulates two payoff strategies month by month, side by side. Every debt receives its minimum payment; then all remaining money is funnelled into one target debt. When that debt clears, its payment rolls into the next target, which is where the "snowball" acceleration comes from.
The only difference between the two strategies is which debt gets the extra money first:
- Debt avalanche targets the highest interest rate first. This is mathematically guaranteed to minimize the total interest you pay.
- Debt snowball targets the smallest balance first. It usually costs a little more interest, but it clears individual debts quickly, and those visible wins keep many people motivated enough to finish.
When avalanche beats snowball — and when it does not
The avalanche always saves the most money; that is not in dispute. What matters is how much it saves in your specific situation. When one or two debts carry much higher rates than the rest — a credit card at 24% sitting next to loans at 5% — the avalanche can save a meaningful amount, and it is worth the discipline. But when your debts have similar rates, the two methods finish within a month or two of each other and cost nearly the same. In that case the snowball is a perfectly rational choice, because the strategy you actually stick with is the one that works.
Seeing the trade-off
A warning the calculator gives you
If your total monthly payment is smaller than the interest accruing across your debts each month, the balances grow no matter how long you pay. When that happens, the calculator flags it rather than showing an impossible payoff date — a sign you need to increase the minimums, add more to the extra payment, or look at options like a lower-rate balance transfer.
For the full comparison of the two methods, read debt snowball vs. avalanche, and to understand why paying only the minimum is so costly, see the minimum-payment trap.
Frequently asked questions
Snowball or avalanche — which is better?
Avalanche (highest APR first) always minimises total interest; that is mathematically guaranteed. Snowball (smallest balance first) clears individual debts sooner, which many people find more motivating. This calculator runs both so you can see exactly what the difference costs in dollars and months.
What does the extra payment do?
Every debt receives its minimum payment first. Whatever is left over — your extra amount — is funnelled entirely into one target debt chosen by the strategy. When that debt clears, its payment rolls into the next target.
Why does it warn that my balances would grow forever?
If your total monthly payment is smaller than the interest accruing each month, the balances increase no matter how long you pay. When that happens the calculator flags it instead of showing an impossible payoff date.