Define what the comparison leaves out
The snowball approach prioritises the smallest balance for extra repayment; the avalanche approach prioritises the highest interest rate. Both generally involve maintaining required payments on the other included debts. The CFPB describes these two broad methods. They are not a substitute for dealing with unaffordable required payments, arrears with serious consequences or jurisdiction-specific priorities.
Our example contains two fictional balances, no fees, no new borrowing and no changes to rates. Interest is charged once per month before payments. Required payments are fixed for the example, even though real minimum payments may change. The example compares the first step and the following month's interest, not the complete repayment period.
Give both methods the same payment budget
Debt A begins at $300 and charges 1% monthly interest. Debt B begins at $1,000 and charges 2% monthly interest. The required payments are assumed to be $30 on A and $50 on B, with another $100 available for extra repayment. Both methods therefore use $180 in the first month.
The first interest charges are $3 on A and $20 on B. After the required payments, the balances are $273 and $970. At this point, the total is $1,243. The next decision is where the extra $100 goes; it is not whether to skip either required payment.
Follow each route for one extra payment
With the snowball approach, the $100 goes to A because A is smaller. The resulting balances are $173 and $970, totalling $1,143. With the avalanche approach, the $100 goes to B because B has the higher rate. The resulting balances are $273 and $870, also totalling $1,143. Immediately after the payments, the same total amount has been repaid.
The next month's interest reveals the difference. Under the snowball route it is $1.73 plus $19.40, or $21.13. Under the avalanche route it is $2.73 plus $17.40, or $20.13. Directing the extra $100 to the balance charging one percentage point more per month saves $1 in that next month's interest under these assumptions.
That is a narrow calculation, not a claim about the exact lifetime saving for a real borrower. Future required payments, rounding, rate changes and fees can affect the full schedule. A complete comparison needs to carry each balance forward until repayment, using the actual rules and the same total payment budget for both methods.
Understand what the smaller-balance approach changes
Paying A first brings that individual account closer to zero sooner. Some people may find a completed balance easier to track or more motivating. That behavioural benefit cannot be inserted into the arithmetic as a guaranteed saving. It is a separate consideration about whether a plan will be followed.
When one balance is repaid, the amount previously directed to it needs an explicit next destination if the overall repayment budget is to remain unchanged. Otherwise a method described as a continuing plan can quietly become a smaller total payment. Check this transition in a schedule rather than assuming it will happen automatically.
Use the example to ask better questions
Before applying either method, confirm the required payments, current rates, special terms and consequences of missed payments. Check whether additional payments incur charges or are allocated as expected. Promotional rates ending soon can also change a ranking based only on today's figures.
If the payment budget itself is not sustainable, revisit that issue first and obtain appropriate local help. The useful lesson from this example is the distinction between total principal repaid now, interest charged later and the practical ability to maintain the plan. No single label answers all three.
