Snowball vs avalanche, on the same debts.

1. The mechanics, side by side

Snowball. Order debts smallest balance to largest. Pay minimums on all of them. Throw every spare dollar at the smallest. When it’s gone, roll its minimum payment into the focus payment on the next-smallest. Repeat until done.

Avalanche. Order debts highest APR to lowest. Pay minimums on all of them. Throw every spare dollar at the highest-APR debt. When it’s gone, roll its minimum payment into the focus payment on the next-highest-APR. Repeat until done.

The only difference is the ordering. The cascade mechanic is identical: freed-up minimum payments roll forward as each debt clears.

2. Worked example: typical household debt mix

Three debts: a $850 store card at 26.99 % APR with a $35 minimum; a $2,400 Visa at 22.99 % APR with a $75 minimum; a $9,200 auto loan at 6.5 % APR with a $240 minimum. Available extra payment: $100/month.

Snowball ordering (smallest first): store card → Visa → auto. Total months to debt-free: approximately 30. Total interest paid: approximately $2,290.

Avalanche ordering (highest APR first): store card → Visa → auto. Total months: approximately 30. Total interest: approximately $2,260.

In this example the orderings happen to coincide because the smallest balance is also the highest APR. The dollar difference is small ($30) because the highest-APR debt and the smallest debt are the same debt. Snowball and avalanche only diverge when the smallest debt and the highest-APR debt are different debts.

3. Worked example: when the methods diverge

Three debts: a $4,500 personal loan at 11 % APR with a $150 minimum; a $1,200 Visa at 24 % APR with a $40 minimum; a $850 store card at 26 % APR with a $35 minimum. Extra: $150/month.

Snowball: store card ($850) → Visa ($1,200) → personal loan ($4,500). Total months: 32. Total interest: $1,140.

Avalanche: store card (26 %) → Visa (24 %) → personal loan (11 %). Identical ordering — both methods pay store card first because it is both smallest and highest-APR.

For genuine divergence, consider this fourth-debt variant: add a $400 medical bill at 0 % APR with a $25 minimum. Snowball orders: medical ($400) → store card ($850) → Visa ($1,200) → personal loan ($4,500). Avalanche orders: store card → Visa → personal loan → medical (last, since it’s 0 %). The snowball clears the medical bill in month 2 with a small win; the avalanche pays minimums on the medical for almost three years. Total interest: snowball ~$1,150, avalanche ~$1,090. Avalanche saves $60 of interest at the cost of pushing the smallest-and-most-tractable debt to last.

4. The empirical literature on completion rates

Northwestern Kellogg School research published in the Journal of Consumer Research (Brown & Lahey, 2014) found that participants in a controlled debt-payoff experiment completed the snowball plan more often than the avalanche plan, with the difference attributable to the motivating effect of early small wins. The effect was strongest among participants who reported lower baseline financial discipline. Subsequent replications have generally confirmed the pattern, with completion-rate gaps in the 5–15 percentage-point range depending on the population.

The implication: the “optimal” method on paper is the one you finish in practice. Avalanche’s mathematical edge is an edge only conditional on completion. A snowball plan that you finish strictly dominates an avalanche plan that you abandon at month 18.

5. Choosing the right method for your profile

Snowball is likely the better choice if:

• You have several small debts and at least one large debt (typical mixed-debt household).
• You have abandoned previous debt-payoff plans before completion.
• You and your partner need visible early wins to stay aligned on the plan.
• The dollar gap (which the calculator will show) between snowball and avalanche is under a few hundred dollars.

Avalanche is likely the better choice if:

• You have demonstrated discipline on previous multi-year financial commitments.
• Your debt mix has one or two large high-APR balances dominating the picture.
• The dollar gap between methods is meaningful (over $1,000) on your specific debt list.
• You are comfortable waiting many months for the first payoff “win.”

6. The hybrid method

A reasonable compromise: order primarily by APR (avalanche logic) but pull a small early debt forward in the queue to capture the behavioural win. If your highest-APR debt has a $4,000 balance and you also have a $300 medical bill, pay off the medical bill first to score the early win, then proceed with avalanche order on the remainder. Total interest cost is virtually identical to pure avalanche; behavioural completion benefits approximate snowball. This is the working approach Marsha uses in workshop settings.

7. The plan-disruption test

Whichever method you pick, run one stress test before committing: imagine that month 6 brings an unexpected $800 expense (car repair, dental work, plumbing) and you have to skip a month of extra payments. Does the plan recover? Run the calculator with the original parameters minus one month of extra and check whether the new total still feels acceptable. If a single skipped month destroys the morale of the plan, the plan is too tight; reduce the extra payment slightly to build cushion. A plan you can sustain through normal life disruption is a plan you finish.