The two orderings
Both methods work the same way mechanically: pay the minimum on every debt, then throw every extra rupee available at exactly one debt at a time, in a specific priority order. Avalanche orders debts from highest interest rate to lowest — mathematically minimizing total interest paid, since the most expensive debt (in interest terms) is eliminated first. Snowball orders debts from smallest balance to largest — delivering a fully paid-off debt sooner, which many people find motivationally powerful even when it isn't the mathematically optimal order.
A worked example showing genuine divergence
Two debts: ₹20,000 at 8% (small balance, low rate) and ₹1,00,000 at 24% (large balance, high rate), with ₹3,000/month extra available beyond minimum payments. Avalanche attacks the 24% debt first despite its larger balance, reaching debt-freedom in 21 months while paying about ₹24,400.60 in total interest. Snowball attacks the smaller ₹20,000 debt first despite its lower rate, reaching debt-freedom in the identical 21 months but paying about ₹27,069.42 in total interest — about ₹2,668.82 more, purely from the different payoff order.
Why the payoff timeline can match even when interest differs
In this example, both strategies take the same 21 months to reach debt-freedom — the difference shows up entirely in how much interest accumulates along the way, not in how long the process takes. This isn't true for every combination of debts; depending on the specific balances, rates, and payment amounts involved, avalanche can sometimes finish faster too, but the interest-cost advantage is the more consistent, reliable benefit of the avalanche approach.
Why snowball remains a popular recommendation anyway
Snowball's appeal isn't mathematical — it's behavioral. Eliminating a small debt entirely, even an inexpensive low-interest one, produces a concrete, visible win early in the process, which many people find sustains motivation through a long debt-payoff journey better than avalanche's approach of tackling the largest or highest-rate debt first (which may take much longer to show a "won" debt, even though it's saving more money along the way).
Choosing between them
If staying motivated and disciplined through the full payoff process is the harder part for you personally, snowball's early wins may be worth its typically-higher total interest cost. If you're confident in your ability to stick with a plan regardless of early visible progress, avalanche's lower total interest makes it the mathematically better choice. Both strategies genuinely work — the "best" one is ultimately whichever one you'll actually follow through to completion.