Debt Snowball vs Avalanche: Same Four Debts, Two Orders, Real Numbers

The two strategies in one paragraph each

With the avalanche method, you pay the minimum on everything and throw every spare dollar at the debt with the highest interest rate. When it is gone, you move to the next highest. It minimizes total interest, mathematically, because you are always attacking the most expensive money first.

With the snowball method, you do the same but target the smallest balance first, regardless of rate. It costs more in theory, but you finish individual debts sooner, which some people find motivating enough to keep going. The argument for it is behavioral, not arithmetical. So how much does that behavioral advantage cost? Let us run it.

The test debts

Here are four invented debts that add up to 19,700, with a fixed payment on each (treat these as the minimums):

• Store card: 900 at 26.99%, payment 35
• Credit card: 6,200 at 23.99%, payment 140
• Car loan: 9,500 at 7.5%, payment 260
• Personal loan: 3,100 at 14.5%, payment 110

The minimums add up to 545 a month. Now we add an extra 300 a month, so the total budget is 845. Whenever a debt is cleared, its payment rolls into the next target. Both strategies get the same 845 every month, and interest is computed monthly.

The results

• Avalanche: debt-free in 27 months, total interest about 3,075
• Snowball: debt-free in 28 months, total interest about 3,339

The gap is 264 and one month. For people who expected a dramatic difference, that is anticlimactic. On roughly 20,000 of debt, the optimal method saves about 1.3% of the starting balance compared with the behavioral one. Try it with an extra 150 a month instead of 300 and the picture is similar: both take 35 months, and avalanche saves about 286 (4,290 versus 4,576).

Here is what changes more than the totals: the order in which debts disappear.

• Avalanche: store card gone in month 3, credit card in month 18, personal loan in month 21, car loan in month 27
• Snowball: store card gone in month 3, personal loan in month 10, credit card in month 22, car loan in month 28

Under snowball, the second victory arrives in month 10 instead of month 21. That is eleven months sooner, which is the real selling point. Under avalanche, the 6,200 card, the most expensive large debt, gets cleared four months earlier. Both approaches clear the store card in month 3 because in this example it happens to be both the smallest balance and the highest rate. When those two properties coincide, the strategies behave identically at the start.

When the gap gets wide, and when it vanishes

The size of the penalty for choosing snowball depends on two things. First, how far apart your rates are. If all your cards are charging between 22% and 25%, the order barely matters. If you have a 29% card with a large balance and a 5% loan with a tiny one, snowball means leaving the 29% debt compounding while you clear the cheap one. Second, how large the extra payment is. With no extra money at all, both methods took 51 months in this test, with interest of about 7,658 for avalanche and 7,687 for snowball, a difference of only 29. The extra money is what gives the ordering room to matter.

The mechanics are worth keeping in mind. Both methods depend on rolling freed-up payments forward into the next target. Without that rule, the car payment and the card payments each end on their own schedule and the money simply returns to your monthly budget. Rolling is the engine. The target order is the steering.

How to choose

Some practical guidance, based on the numbers above and on how people actually behave:

• If your highest-rate debt is also large, go with avalanche. Leaving a 24% card for two extra years while you clear small cheap balances is the one situation where snowball costs real money.
• If you have many small balances, or you have tried and abandoned a payoff plan before, snowball's early wins are worth a few hundred dollars. A plan you finish beats a perfect plan you quit.
• Consider a hybrid. Clear one tiny debt first for momentum, then switch to highest-rate order for the rest.
• Always check for a better lever than ordering. A balance transfer at a promotional rate or a debt consolidation loan that cuts the rate on everything can be worth more than either method, provided the fees and the terms hold up.

What this simulation leaves out

Real life has more moving parts than a clean model. Payments here are fixed and no new charges appear, whereas a card you keep using will refill. Variable rates can rise, which can change which debt is the most expensive halfway through. Some debts have prepayment penalties or promotional rates that end on a specific date: a 0% balance that jumps to 25% in month 9 belongs near the top of your list as that date approaches, whatever its current rate says. And a few debts, like some low-rate student loans, come with protections or tax treatment that can justify paying them last. Treat the plan as something you review every few months, not a script you follow blindly.

Run your own debts

The figures above come from a month-by-month simulation, and your balances and rates are surely different. The debt payoff calculator lets you enter each debt and compare the orders directly. For a single card, the credit card payoff calculator shows how long a given payment takes and what it costs.

Before you pick, make one more decision: how much extra can you really commit, and for how long? A realistic 150 held for 35 months beats an optimistic 400 abandoned in month 6. The best strategy is the one whose payment you can still make during a bad month.