Debt avalanche calculator

Run the avalanche against the snowball on the same debts and the same budget. You get the interest saved and the months saved — and, more usefully, whether the gap is big enough to care about.

How the math works

Both methods pay the minimum on every debt and throw whatever is left of your budget at one target debt. The only thing they disagree on is which debt.

Each month, interest accrues on every balance at its APR divided by 12. Minimums go out first. The leftover — your extra — lands entirely on the target. When a debt clears, its freed-up minimum joins the extra, so the amount hitting the next target grows. That rollover is why both methods speed up as they go, and it's identical in each. The order is the whole difference.

The avalanche is the order that pays the least total interest. That's not a claim, it's arithmetic: retiring a dollar of 22.76% debt stops more interest than retiring a dollar of 6.53% debt, so front-loading the high rates always costs less. The snowball ignores rate and chases the smallest balance, which clears whole accounts faster but leaves the expensive balances accruing longer.

Worked example

Take a household carrying three debts and putting $1,500 a month toward all of them combined:

• A credit card: $6,500 at the U.S. average APR of 22.76%.
• A student loan: $27,000 at the 2024–25 federal undergraduate rate of 6.53%.
• An auto loan: $32,000 at the average new-car rate of 8.40%.

The card is both the smallest balance and the highest rate, so both methods kill it first. After that they split. The avalanche goes card, then auto (8.40%), then student loan (6.53%). The snowball goes card, then student loan ($27,000), then auto ($32,000).

Both clear the whole $65,500 in 52 months. The avalanche pays $11,753.06 in interest; the snowball pays $12,231.33. The avalanche wins — by $478.27 and zero months. Over more than four years of payments, that's under ten dollars a month. On this debt mix, the two methods are, for practical purposes, the same plan.

That is the number the side-by-side calculators show but rarely interpret. Sometimes the answer to "which method" is "it genuinely does not matter, pick the one you'll stick with."

When this calculator is wrong

The calculator is arithmetically correct. Where it misleads is in how much weight it invites you to put on the answer.

• The gap is usually small — until one condition flips it. The avalanche's edge only gets large when a wide APR spread sits on a big high-rate balance. Move the worked example's numbers so the 22.76% card holds $32,000 and the 6.53% loan holds $6,500, keep a $1,200 budget, and the avalanche now saves $4,282.54 and three months. Same two methods, a ten-times-bigger prize. The size of the high-rate balance, not the mere existence of a rate difference, is what decides whether the choice is worth agonizing over.
• Close APRs make it a coin flip. When your debts sit within a couple of points of each other, the avalanche and snowball land within a rounding error. The calculator will still name a winner to the penny, which reads as precision. It isn't. It's noise.
• The avalanche only wins if you finish. The math assumes you keep paying the same budget for 52 months without wavering. The snowball clears whole accounts sooner, and for a lot of people those early wins are what keep the payments going. A method you abandon in month 18 loses to one you finish. If you know which kind of payer you are, that should outweigh the interest column.
• It assumes fixed rates, fixed minimums, and no new borrowing. A variable-APR card, a single new purchase, or a missed payment resets the schedule. The projection models a closed system; a real balance sheet isn't one.

The honest framing: use the calculator to find out whether you're in the "it barely matters" case or the "it's worth a few thousand dollars" case. That single question is more useful than the winner it names.

What to do with the result

If the interest saved comes back small — a few hundred dollars over years — stop optimizing and start paying. Pick the order you will actually sustain, automate the budget so the extra can't quietly get spent, and don't reopen the question. The gap between avalanche and snowball is smaller than the gap between paying the extra and not.

If the interest saved comes back large, you're in the wide-spread case, and the avalanche is worth the discipline it asks for. Point every spare dollar at the highest-APR balance, hold the total payment flat as balances fall, and let the rollover do its work. Either way, the number that moves your payoff date most is the size of the monthly budget — raise that before you fine-tune the order.

Common questions

Is the debt avalanche always better than the snowball?

On interest, yes — the avalanche pays the least by definition, because it retires the highest-rate debt first. But "better" depends on whether you finish. The snowball's early wins help some people stay on plan, and a method you complete beats a cheaper one you quit. On the math alone, the avalanche wins; in practice, the best method is the one you'll actually run to zero.

How much does the debt avalanche actually save?

Often less than people expect. On a mixed load of a $6,500 card at 22.76%, a $27,000 student loan at 6.53%, and a $32,000 auto loan at 8.40%, paying $1,500 a month, the avalanche saves $478.27 and zero months over the snowball. The gap only gets large when a big balance carries the highest rate.

What's the difference between the avalanche and the snowball?

Order, and nothing else. Both pay minimums everywhere and pile the leftover onto one target debt. The avalanche targets the highest APR; the snowball targets the smallest balance. When the smallest balance is also the highest rate, the two methods are identical.

Should I pay the minimum on my other debts while I attack one?

Yes. Both methods require paying every minimum every month — that's what keeps the other accounts current. The strategy is only about where the extra money goes, not about skipping payments. Miss a minimum and you add fees and rate hikes the calculator never sees.

Does the avalanche pay everything off faster?

Not necessarily. Because both methods spend the same budget, they often finish in the same month; the avalanche's advantage usually shows up as less interest rather than fewer months. In the worked example both plans finish in 52 months — the avalanche just pays less along the way.