You have four debts. You have $500 extra this month to put toward them. Which one gets it?
If you choose based on instinct — the biggest balance, the most stressful creditor, the one you've had longest — you're almost certainly leaving money on the table. Payoff order has a dramatic effect on total interest paid and total time in debt. Here's the math.
A Real Example
Let's say you have:
- Credit card A: $3,000 at 24% APR, $75 minimum
- Credit card B: $8,000 at 18% APR, $180 minimum
- Car loan: $12,000 at 6% APR, $220 minimum
- Student loan: $15,000 at 5.5% APR, $160 minimum
Total debt: $38,000. Total minimum payments: $635/month. You have $500 extra to allocate.
Strategy 1: Minimum Payments Only
Time to payoff: approximately 8-9 years (as balances and minimums slowly decline).
Total interest paid: approximately $14,000.
Strategy 2: Random Extra Payments (split across accounts)
Spreading $500 across all accounts proportionally each month.
Time to payoff: approximately 5 years.
Total interest: approximately $9,500.
Strategy 3: Avalanche (highest rate first)
$500 extra on Card A (24%), then B (18%), then car, then student loan.
Time to payoff: approximately 4.5 years.
Total interest: approximately $7,200.
Strategy 4: Snowball (smallest balance first)
$500 extra on Card A ($3,000 balance first), then B, then car, then student loan.
Time to payoff: approximately 4.6 years.
Total interest: approximately $7,900.
What the Numbers Tell You
The difference between random payments and avalanche is $2,300 and roughly 6 months of your life. Not dramatic enough? Compare minimum-only to avalanche: $6,800 in interest savings and 4+ years.
The choice between avalanche and snowball — the two "correct" methods — is a $700 difference. That's relatively small, which is why the psychological argument for snowball (stay motivated, don't quit) is legitimate. But both beat the alternative by thousands of dollars.
The Carry Cost of Low-Rate Debt
Here's what most people get wrong: they assume the car loan and student loan can wait indefinitely because their rates are low. But low-rate debt still has a carry cost, and more importantly, keeping high-rate debt alive while you "work toward" low-rate debt is extremely expensive.
Every month you're paying 24% on Card A, you're losing roughly $60 in interest. Every month you delay attacking it is $60 that doesn't go toward your principal. The order isn't about which debt feels most urgent — it's about which one is costing you the most per month.
Calculate Your Order
List every debt with its balance and APR. Sort by APR from highest to lowest. That's your avalanche order. If the highest-rate debt also happens to be your largest balance, consider whether a quick snowball win on a small debt might give you the psychological fuel to commit to the longer fight — then switch to avalanche order.