The avalanche method: why it saves the most on student loans

If you have extra money to put toward student loans and more than one loan to choose from, the order you pay them in changes how much interest you hand over. The avalanche method is the mathematically cheapest order. Here is why, a worked example, and the one situation where it backfires.

How the avalanche method works

The avalanche method directs every extra dollar at your highest-rate loan first, while paying the minimum on everything else. When the highest-rate loan is gone, you roll its whole payment into the next-highest-rate loan, and so on down the line. The order is set strictly by interest rate, not by balance, and the rolled-up payment is what makes the later loans fall faster and faster.

9.25%Extra goes here first

7.10%Minimum only

5.50%Minimum only

4.99%Minimum only

Illustrative: pay the minimum on every loan, then send every spare dollar to the highest rate. Clearing the most expensive debt first saves the most interest, mathematically.

A worked example

Say you have four loans and $300 a month of extra money beyond the minimums. Avalanche says ignore the balances and rank by rate.

Loan	Rate	Order to attack
Private A	9.25%	1st, all extra goes here
Private B	7.10%	2nd
Federal C	5.50%	3rd
Federal D	4.99%	4th

Pay minimums on all four; send the full $300 extra to the top row first.

When Private A is paid off, its minimum plus your $300 rolls onto Private B, then onto Federal C, and so on. Each loan you finish frees up a larger payment for the next, which is why the last loans disappear quickly even though you started small.

Illustrative: the worked example with minimums of $52, $48, $45, and $40 on loans A through D, plus your $300 extra. Every retired loan hands its minimum to the next attack, so the payment aimed at the current target climbs from $352 to $485 while the stack shrinks from four loans to one. The attack never shrinks; it grows, which is why the last loans fall fastest.

Why it saves the most

The highest-rate loan costs you the most for every day it exists, because interest accrues fastest on it. Killing that loan earlier means less interest builds up in all the months that follow. Every dollar you send to a 9% loan saves more than the same dollar sent to a 5% loan, so the avalanche always sends dollars where they save the most.

Illustrative: the yearly interest on the same $10,000 at each loan's rate from the worked example. An extra dollar aimed at a loan earns a guaranteed return equal to that loan's rate, so a dollar on the 9.25% loan beats the same dollar anywhere else in the stack. That is the entire avalanche argument in one picture.

Avalanche vs snowball

	Avalanche	Snowball
Attacks first	Highest interest rate	Smallest balance
Optimizes for	Least total interest paid	Fastest first payoff (motivation)
Total cost	Lower	Higher
Best for	Saving the most money	Needing quick visible wins

Both work. Pick avalanche to save the most, snowball if early wins keep you going.

The one place avalanche backfires

If one of your loans is a federal loan on the new RAP plan, paying extra can cancel that month’s interest subsidy and principal match, which undoes the benefit. So the avalanche order applies to the rest of your stack: pay the RAP minimum, then aim your extra dollars at the highest-rate loan among everything else, which is usually a private balance anyway.

Build your loan strategy

Sources

Standard amortization math; see your amortization schedule for an exact picture.
U.S. Dept. of Education, RAP implementation rule (Federal Register, 2026)