Ask around and you'll get two different answers to the same question: what order should you pay off debt in? One camp says smallest balance first, for the win. The other says highest interest rate first, for the math. Both are describing something real. They just disagree about what actually gets someone out of debt.
The debt snowball sorts by balance, smallest to largest, and throws every extra dollar at the smallest one until it's gone. The debt avalanche sorts by interest rate instead, highest to lowest, on the theory that whatever's compounding the fastest should get paid down first.
Neither is wrong. They're optimizing for two different things, and the honest answer to "which one should I use" depends on which of those two things matters more to you.
What each method optimizes for
Avalanche optimizes for total cost. Interest is compounding fastest on the highest-rate debt, so paying it down first stops the most expensive growth first. Run the math on nearly any real set of debts and avalanche comes out ahead in total interest paid, sometimes by a little, sometimes by a lot depending on how spread out the rates are.
Snowball optimizes for something math doesn't measure directly: whether the person doing the paying keeps doing it. Clearing an entire debt off the list, even a small one, is a different kind of progress than watching a total balance get smaller. It's visible, it's final, and for a lot of people it's the difference between staying motivated through month eighteen and quietly stopping around month six.
Snowball vs. avalanche, side by side
| Snowball | Avalanche | |
|---|---|---|
| Sorts debts by | Balance, smallest first | Rate, highest first |
| Optimizes for | Early wins, momentum | Total interest paid |
| First debt usually clears | Sooner | Later |
| Total cost over time | Usually more | Usually less |
| Works best if | You need to see progress to keep going | You trust the math and can wait for the win |
A middle option most comparisons skip
The choice isn't strictly one or the other. A common middle ground: if one debt is both small and low-priority under a strict avalanche order, some people clear it first anyway, purely for the early win, then switch to a strict highest-rate-first order for everything left. It costs a little in total interest and buys back some of the momentum snowball is built around. Whether that trade is worth it depends on how much that first win is actually worth to you.
A real example, side by side
Say there are three debts: a credit card at $4,200 and 24.99% APR with a $105 minimum, a car loan at $9,800 and 6.5% APR with a $310 minimum, and a personal loan at $2,100 and 13% APR with an $85 minimum. There's $200 extra to put toward debt each month on top of the minimums.
Snowball sorts by balance: personal loan ($2,100) first, then credit card ($4,200), then car loan ($9,800). The personal loan clears fastest, and that $85 minimum rolls forward into whichever debt is next in line.
Avalanche sorts by rate: credit card (24.99%) first, then personal loan (13%), then car loan (6.5%). The credit card takes longer to clear than the personal loan would have, but less total interest accrues along the way, since the most expensive balance stops growing first.
Run the actual numbers on a set of debts like this and avalanche usually wins on total interest paid, sometimes by a little and sometimes by a lot depending on how spread out the rates are. Snowball usually wins on time to first debt cleared. Both are true at the same time, which is exactly why this isn't a question with one right answer.
Why this is hard to track by hand
The tricky part isn't picking an order, it's tracking what happens after the first debt clears. That $85 or $105 minimum doesn't disappear, it rolls forward into whichever debt is next, which changes that debt's own payoff timeline, which changes the one after it. A spreadsheet can technically model this, but keeping it accurate every time a rate changes or a payment gets missed is exactly the kind of manual math that goes wrong quietly. Some of the ways that math can go wrong aren't obvious until a plan has already been built around the wrong number.
Downslope runs both orders against your actual balances and rates, rolls minimums forward automatically as each debt clears, and shows the real payoff date and total interest for each side, so the comparison in the table above isn't an estimate, it's your own numbers.
What changes once the last debt clears
Somewhere in most payoff plans there's a month where the last minimum payment rolls forward into nothing, because there's nothing left to pay it toward. That's a bigger shift than it sounds like on paper: money that's been earmarked for debt every month suddenly isn't earmarked for anything. What happens to that cash flow matters more than people expect, since it's easy for it to quietly disappear into everyday spending instead of going toward whatever came after debt on the original plan, savings, a bigger emergency fund, or something else entirely.
Switching partway through costs less than people think
A common worry: picking one order, sticking with it for eight months, then wanting to switch. People sometimes stay on a plan they've stopped believing in simply because they assume switching means starting over.
It doesn't. Whatever's already been paid down stays paid down. Switching from snowball to avalanche partway through just means re-sorting whatever's left by rate instead of balance, the progress already made doesn't reset. The only real cost is whatever extra interest accrued during the months spent on the order that wasn't optimizing for it, which for most people is small compared to the cost of abandoning a payoff plan altogether out of frustration with the order chosen.
How to actually decide
Sort your real debts both ways, even roughly. Note two things: how many months until the first debt clears under each order, and roughly how much total interest each order costs over the life of all your debts. If those two numbers are close, the decision mostly comes down to which kind of progress you trust yourself to stay motivated by. If they're far apart, that gap is worth knowing before picking either one.
For the mechanics of actually building either tracker by hand, the debt snowball walkthrough and debt avalanche walkthrough both go through it step by step.
For a deeper, chapter-by-chapter treatment of this comparison and everything around it, extra-payment math, refinancing, credit, life after the last payment clears, Debt Payoff & Credit, a companion textbook in the Downslope Finance Foundations series, is in production now.
Which matters more to you right now, paying less overall, or seeing a debt disappear sooner?