How This Calculator Works
Add every debt you're tracking — its name, current balance, monthly (or minimum) payment, and interest rate. The calculator simulates your payoff month by month: each month it charges interest on every open balance, applies each debt's minimum payment, then sends any leftover money — your extra payments plus whatever surplus is left after minimums — to whichever debt currently has the highest interest rate. That's the debt avalanche method, and it's mathematically the cheapest way to clear multiple debts. The result shows your exact debt-free month, total interest paid, the order your debts get wiped out, and a chart of your combined balance shrinking to zero over time.
The Debt Avalanche Method Explained
Every month, the avalanche method pays the required minimum on all your debts, then throws every extra dollar at the single debt charging the highest interest rate — regardless of its balance. Once that debt hits zero, the next-highest-rate debt becomes the new target, and the process repeats until everything is paid off. Because your money always attacks whichever balance is costing you the most in interest, this method minimizes the total interest you pay across all your debts combined, compared to any other payoff order.
Extra Payments: Monthly, Yearly, and One-Time
Beyond your regular minimums, the calculator lets you model three kinds of extra money: a recurring extra per month (like committing an additional $100 every payment cycle), a recurring extra per year (useful for an annual bonus you plan to put toward debt), and a one-time extra applied in a specific month you choose — handy for modeling a tax refund, a bonus, or money from selling something. All three get folded into the avalanche logic automatically and directed to your current highest-priority debt in the month they land.
Fixed vs. Declining Total Payment
The "Fixed total monthly payment" toggle controls what happens once one of your debts is fully paid off. Set to Yes, the amount you were paying toward that finished debt doesn't disappear — it gets folded into your budget and redirected to your next highest-rate debt, so your total monthly outlay stays constant and your remaining debts get paid off faster. Set to No, your total monthly payment shrinks by that debt's payment amount once it's gone, which is gentler on your budget in the short term but always results in a longer payoff timeline and more total interest.
Debt Avalanche vs. Debt Snowball
The debt snowball method is the other popular payoff strategy: instead of targeting the highest interest rate, it directs extra payments at your smallest balance first, regardless of rate. Snowball tends to clear individual debts faster early on, which many people find motivating — each payoff feels like a quick win. The tradeoff is that snowball usually costs a bit more in total interest than avalanche, since it isn't optimizing for rate. This calculator uses avalanche, the mathematically cheaper approach, but if the psychological momentum of snowball matters more to you, either strategy will get you to zero — the difference is usually a modest amount of extra interest, not a different outcome.
How Much Extra Payments Actually Save You
Because avalanche sends every extra dollar straight to your highest-rate balance, extra payments are disproportionately powerful early in a high-interest debt's life — that's when the balance (and therefore the interest it generates every month) is largest. The "Interest saved" and "Time saved" figures in your results compare your current extra-payment plan against making only minimum payments, so you can see concretely what committing an extra $50, $100, or more per month is actually worth in dollars and months, not just in theory.
Common Mistakes When Paying Off Multiple Debts
A common mistake is spreading extra money evenly across several debts instead of concentrating it on the highest-rate one — that feels balanced but costs more in total interest than committing everything to a single target. Another is ignoring the "fixed total payment" choice entirely; letting your total monthly budget shrink every time a debt disappears quietly extends your payoff timeline. A third is underestimating how much a modest recurring extra payment compounds over time — the gap between $0 extra and even $50–100 a month is often much larger than people expect, especially on high-rate credit card debt. Finally, watch for a debt whose minimum payment doesn't even cover its own monthly interest — that balance will never shrink on its own no matter how patient you are, and needs either a larger payment or avalanche priority to make real progress.
Card debt is usually where this starts. Our credit card calculator shows what the minimum payment really costs, and the credit card payoff calculator puts a date on clearing the balance.
Frequently Asked Questions
What is the debt avalanche method?
The debt avalanche method pays the minimum on every debt, then directs all extra money toward the debt with the highest interest rate. Once that debt is paid off, the extra shifts to the next-highest-rate debt, and so on. Mathematically, it's the fastest and cheapest way to become debt-free — this calculator uses it by default.
What's the difference between debt avalanche and debt snowball?
Avalanche targets the highest interest rate first, which minimizes total interest paid. Snowball targets the smallest balance first regardless of rate, which pays off individual debts faster and can build motivation, usually at the cost of a bit more total interest. Neither is objectively wrong — pick the one you're more likely to stick with.
What does "Fixed total monthly payment" actually change?
When it's on, the total amount you were paying across all debts stays the same even after one debt is paid off — that freed-up payment gets redirected to your next debt, accelerating payoff. When it's off, once a debt is paid off you simply stop paying that portion, and your total monthly outlay shrinks. Fixed total payment always pays off debt faster and cheaper.
How much do extra payments actually help?
Often a lot, especially on high-interest debt. Because extra payments go straight to principal on your highest-rate balance, even a modest amount — $50 or $100 a month — can cut months or years off your payoff timeline and save hundreds or thousands in interest. Try adding an extra payment in the calculator and compare the totals.
Should I include a one-time extra payment like a tax refund or bonus?
Yes, if you're planning to use it that way — enter the amount and the month number you expect to receive it. The calculator applies it in that specific month to whichever debt is currently receiving avalanche priority, which is usually the most efficient use of a lump sum.
Why does my highest-rate debt sometimes get paid off before a smaller one?
It might not, and that's expected — the avalanche method sends surplus money to the highest-rate debt, but a debt with a very small balance can still finish first just from its own minimum payments if it doesn't need much time to reach zero on its own, independent of any extra it receives.
What if a debt shows it will never be paid off?
That means the payment entered for that debt doesn't even cover the monthly interest charge, so the balance would grow indefinitely under those numbers. You'll need either a higher payment on that debt or extra funds directed its way to make real progress.
Does this calculator account for daily compounding on credit cards?
It applies your annual rate once per month against the remaining balance, which is the standard simplification most payoff calculators use. It comes very close to daily compounding for typical balances and rates — usually within a small margin over a full payoff timeline.
This calculator provides general estimates only. It is not financial advice — confirm your exact balances, rates, and payment terms with your actual lenders.