Debt payoff calculator: snowball vs avalanche

What are the debt snowball and debt avalanche methods?

Both methods start the same way: pay the minimum on every debt, every month, no exceptions. The difference is where any extra money you have beyond the minimums goes.

• Debt snowball: the extra goes to the debt with the smallest balance, regardless of its interest rate. Once it's paid off, its minimum payment rolls into the extra amount, and the whole pile moves to the next-smallest balance.
• Debt avalanche: the extra goes to the debt with the highest APR (annual percentage rate, the yearly cost of borrowing), regardless of its balance. Same rolling mechanic, but the target is the costliest debt instead of the smallest one.

The Consumer Financial Protection Bureau (CFPB) describes both this way: the smallest-balance approach lets you "see progress quickly" but "you may end up paying more in the long run," while the highest-rate approach targets the debt "costing you the most" and will "save you money in the long run." The CFPB does not tell consumers which to pick; it frames the choice around what keeps you motivated to keep paying.

Try it: your debts, both strategies

Enter up to five debts (balance, APR, and minimum payment) and how much extra you can put toward debt each month. The calculator simulates both strategies month by month: it adds interest to every open balance first, then pays each debt's own minimum, then puts whatever is left, the extra amount plus any minimum payments freed up by debts you've already paid off, toward the priority debt for that strategy.

Extra amount you can put toward debt each month

Avalanche saves $213 in interest versus snowball with these numbers (25 vs 25 months to debt-free, same total budget either way). Label: estimate. Assumes fixed monthly payments, interest compounding monthly on the statement balance, and no new charges or missed payments.

Which method saves more money, snowball or avalanche?

Avalanche always saves the same amount of interest or more than snowball, because it always attacks the debt with the highest cost of carrying a balance first. It never saves less. How much it saves depends entirely on how much the balances and rates diverge from a strict smallest-to-largest ordering. In the sample above, avalanche saves about $213 in interest across 25 months, roughly 12% less total interest than snowball, because it goes after the 22% credit card balance eight months sooner than snowball does.

The gap can be much bigger or close to zero depending on the numbers. If your smallest balance also happens to carry your highest APR, the two methods pick the exact same order and cost the exact same amount. If your smallest balance carries your lowest APR, as in the example above, the gap widens because snowball spends months paying down cheap debt while expensive debt keeps accruing interest.

Why is the avalanche method mathematically optimal?

Interest is charged as a percentage of whatever balance is still outstanding, so every month a high-APR balance sits unpaid, it costs more than the same dollar sitting in a low-APR balance. Sending extra money to the highest-rate debt first minimizes the total interest that accrues across all your debts combined, for the same reason it's always cheaper to pay down your most expensive loan before your cheapest one. This holds regardless of the specific balances or rates; it's a property of how compound interest works, not a rule of thumb.

Worked example, month 1 (avalanche): the $5,000 credit card at 22% APR accrues $5,000 × 0.22 ÷ 12 = $91.67 in interest before any payment is applied. The $8,000 auto loan at 6.5% accrues $43.33, and the $2,000 personal loan at 10% accrues $16.67. After each debt gets its own minimum ($125 + $180 + $70 = $375 total), the $300 extra goes entirely to the credit card, since it has the highest APR, bringing its month-1 payment to $425 and its new balance to $5,000 + $91.67 - $425 = $4,666.67. Under snowball, that same $300 would go to the $2,000 personal loan instead (the smallest balance), leaving the 22% card to keep accruing interest for months longer.

Why does the snowball method still work for a lot of people?

Because paying off debt is as much a behavior problem as a math problem, and snowball is built around behavior. A 2012 study in the Journal of Marketing Research by David Gal and Blakeley McShane analyzed roughly 6,000 debtors in a national debt-management program and found that closing accounts, not the dollar balance of the accounts closed, was what predicted whether someone eliminated all their debt. People who reduced their number of open debts faster were significantly more likely to become debt-free, independent of the interest-rate math. The psychological lift of crossing a debt off the list entirely, even a small one, appears to sustain the motivation to keep going.

That is the trade-off in one sentence: avalanche is never worse and often better on total interest paid; snowball is never worse and often better on sticking with the plan long enough to finish. If you already know you'll follow through no matter what, avalanche has no downside. If you've stalled out on debt payoff before, the faster first win from snowball may be worth the extra interest.

How do extra payments and rolling minimums speed up payoff?

Two mechanics do almost all the work. First, any extra amount above your combined minimums goes entirely toward principal on the target debt, so it shrinks the balance that future interest gets charged on, compounding the savings every month it's applied. Second, once a debt is paid off, its minimum payment does not disappear, it rolls into the pool of money attacking the next target. That rolling effect is why payoff accelerates near the end: by the last debt standing, you're often putting your entire original budget (all your old minimums plus your extra) against one shrinking balance.

This is also why utilization and payoff intersect: paying down a card's balance faster lowers the card's contribution to your credit utilization, which can raise your score well before the debt itself is gone. If a card's rate is high enough, it's also worth checking whether a balance transfer to a lower-rate card would cut the interest further before you start either strategy.

What if I can't cover the minimums, or want to change strategies partway through?

The calculator assumes you keep paying the same total budget (minimums plus extra) every month; it cannot recover a debt whose minimum payment doesn't even cover its monthly interest, since the balance would grow forever under either strategy. If that's your situation, the immediate priority is raising the payment on that specific debt, not choosing a strategy. Switching strategies partway through is fine mathematically: re-enter your current balances and rerun the calculator to see the plan from where you actually stand today.

The flat truth on snowball vs avalanche

Avalanche is the correct answer if the only thing you're optimizing for is total dollars paid. Snowball is a reasonable answer if the honest risk is quitting partway through. Neither method works if the extra payment column is $0 and you're only ever paying minimums, since the calculator's benefit comes from the extra money, not from the order you attack debts in. Whichever you pick, the fastest lever you actually control is the size of the extra payment, not which debt it lands on first. If your score matters as much as the payoff itself, see how to improve your credit score for how utilization and payment history interact with paying down debt.