The short answer
The debt avalanche (highest interest rate first) always costs the same or less in total interest than the debt snowball (smallest balance first). How much less depends on your debts. In the example below, the avalanche saves about $210 — while the snowball delivers its first paid-off debt 13 months sooner. Both finish on the same day.
That trade-off — a little money versus a lot of momentum — is the whole debate. Here's the math, worked out month by month.
The example: three debts, $300 extra a month
| Debt | Balance | APR | Minimum payment |
|---|---|---|---|
| Personal loan | $1,200 | 8.00% | $50 |
| Credit card | $7,000 | 24.99% | $210 |
| Car loan | $8,500 | 7.50% | $250 |
The minimums add up to $510 a month. On top of that, this person finds an extra $300 a month, for a total payoff budget of $810. Under both methods, every debt gets its minimum each month, the extra goes to one target debt, and when a debt is paid off its minimum rolls into the next target. The only difference is the order:
- Snowball order (smallest balance first): personal loan → credit card → car loan
- Avalanche order (highest rate first): credit card → personal loan → car loan
The results
| Snowball | Avalanche | |
|---|---|---|
| First debt paid off | Month 4 (personal loan) | Month 17 (credit card) |
| Second debt paid off | Month 18 (credit card) | Month 18 (personal loan) |
| Debt-free | Month 24 | Month 24 |
| Total interest paid | $2,487 | $2,277 |
For comparison, putting no extra money toward these debts (just the $510 of minimums, still rolling each freed-up minimum forward) takes 44 months and costs about $5,639 in interest. Either method roughly halves the time and cuts interest by more than $3,000 — the extra $300 a month matters far more than which method you pick.
Why the avalanche wins on interest
Every month, interest is charged on every balance you still carry. The avalanche shrinks the 24.99% credit card first, so the most expensive balance spends the least time accruing interest. The snowball spends its first four months wiping out an 8% loan while the 24.99% card keeps compounding — that's where the extra $210 comes from.
The gap grows when the rates are far apart and the high-rate debt is large. It shrinks to zero when your smallest balance also has the highest rate — in that case both methods choose the same order. (Our debt snowball walkthrough uses exactly that kind of example, where the store card is both the smallest and the most expensive debt.)
Why the snowball still makes sense for many people
In this example the snowball clears a debt in month 4; the avalanche makes you wait until month 17 for the first one. For a lot of people, a year and a half of payments with nothing crossed off the list is exactly when a plan gets abandoned. If the snowball's quick win is what keeps you paying an extra $300 a month, it's the better plan in practice — the method you stick with beats the method that's optimal on paper.
How to choose
- Run both with your real numbers. If the avalanche only saves you a few hundred dollars, choose whichever you'll stick with.
- Pick the avalanche if you have one large, high-rate balance (like a big credit card) and you're confident you'll stay motivated.
- Pick the snowball if you have several small balances you can clear quickly, or you've tried and quit payoff plans before.
- Find more extra money first. As the numbers show, the size of the extra payment beats the choice of method.
Enter your own debts in the Debt Snowball / Avalanche Calculator and switch the strategy back and forth — then copy the share link to save your plan.
All figures were calculated month by month with the same simulation the calculator uses: interest accrues monthly at APR ÷ 12, minimums are paid on every debt, and freed-up minimums roll to the next target.