Debt Snowball vs. Avalanche: What the Research Actually Says
If you've looked into paying off debt, you've seen the argument. The debt snowball says pay the smallest balance first. The debt avalanche says pay the highest interest rate first. Finance bloggers debate it endlessly, each side arguing theirs is the "right" answer.
Fortunately, we don't have to guess. Researchers at Northwestern University's Kellogg School of Management actually studied this — with real data from thousands of people paying off real debt. The results might surprise you.
The two methods, explained
Debt Snowball: Pay minimums on everything. Throw every extra dollar at the smallest balance, regardless of interest rate. When it's gone, roll that payment into the next smallest. The idea is that quick wins build momentum.
Debt Avalanche: Pay minimums on everything. Throw every extra dollar at the highest interest rate. When it's gone, move to the next highest. The math is clear: you pay less total interest this way.
On paper, the avalanche always wins. In practice? It's more complicated.
What Northwestern's Kellogg School found
Professors Blake McShane and David Gal at Kellogg studied approximately 6,000 people enrolled in a debt settlement program. They tracked who actually eliminated their debt and which strategy they followed. The findings were published in the Journal of Marketing Research.
People who tackled small balances first were 14% more likely to eliminate their debt after one year and 43% more likely after four years — compared to those who targeted the highest interest rates.
Source: McShane & Gal, "The Snowball Approach to Debt," Journal of Marketing Research, Kellogg School of Management, Northwestern University.
Why the "wrong" answer works better
The researchers identified the mechanism: psychological momentum. Separate research by Moty Amar and colleagues called it "debt account aversion" — the human desire to reduce the number of outstanding debts, not just the total balance. Paying off a $900 medical bill in month two feels like real progress. That feeling compounds: each eliminated debt makes you more likely to keep going.
The avalanche, by contrast, often means spending months throwing money at a large, high-rate balance without seeing a single debt disappear. Mathematically it's optimal. Psychologically it's a grind. And the data shows people quit grinds.
The method that pays off zero debt is the one you abandon. The Kellogg research suggests the snowball's motivational advantage outweighs the avalanche's mathematical advantage for most people.
When the avalanche actually makes sense
The snowball isn't universally better. The avalanche is worth considering when:
- Your highest-rate debt is also your smallest or close to smallest balance — meaning you get both the mathematical and psychological advantage
- You have a very high-rate debt (24%+) that is generating substantial monthly interest while you ignore it
- You're naturally motivated by math and can stay disciplined for 12+ months without a visible "win"
- The total interest difference between the two methods is significant (thousands, not hundreds)
A real example: $22,000 in debt
| Debt | Balance | Rate | Minimum |
|---|---|---|---|
| Medical Bill | $900 | 0% | $50 |
| Credit Card | $3,200 | 24.99% | $80 |
| Car Loan | $8,400 | 7.9% | $220 |
| Student Loan | $9,500 | 5.5% | $110 |
With $500/month extra beyond minimum payments:
| Method | First debt eliminated | Total payoff | Total interest |
|---|---|---|---|
| Snowball | Month 2 (medical bill) | 38 months | ~$4,120 |
| Avalanche | Month 8 (credit card) | 36 months | ~$3,640 |
The avalanche saves about $480 and finishes 2 months sooner. But with the snowball, you have your first debt gone in month 2. With the avalanche, you're waiting until month 8. For someone who's tried to get out of debt before and quit, that 6-month head start on motivation matters more than $480.
How to decide: three questions
1. Have you tried paying off debt before and quit? If yes, the snowball. The Kellogg data is built on people like you — and it shows the snowball works better for people who need momentum.
2. Is the interest difference more than $500? If the avalanche saves you thousands, the math is harder to ignore. Run both calculations with your actual debts and see the difference.
3. Can you stay motivated for months without a visible win? Be honest with yourself. If yes, avalanche. If no, snowball.
Run both calculations yourself
Forge includes a debt payoff calculator that lets you enter all your debts and toggle between snowball and avalanche to see your exact payoff date and total interest for each method. It also tracks your progress over time as you pay things off — so you can see the snowball rolling or the avalanche building, whichever you choose.