Two different payoff priorities
The debt snowball method targets the smallest balance first while continuing minimum payments on the other debts. The goal is momentum. Paying off a small debt can create a quick win and make the overall plan feel easier to continue.
The debt avalanche method targets the highest interest rate first while continuing minimum payments on the other debts. The goal is math efficiency. If rates are very different, avalanche often reduces total interest compared with targeting the smallest balance first.
Why the best method is not always only math
The avalanche method can be stronger on interest savings, but a payoff plan also has to survive real life. Some people are more likely to stick with a plan if they see debts disappear one by one. For them, the snowball method may be more effective behaviorally even if it is not always the lowest-interest path.
The important part is that extra payment should be intentional. Paying a little extra randomly across several debts may feel productive, but a focused strategy usually makes progress easier to measure.
Minimum payments and extra payment
Most payoff calculators assume minimum payments continue on every debt. The extra payment then goes toward the target debt. When that target is paid off, the amount that was going to it rolls into the next target. This rolling effect is what makes payoff plans accelerate over time.
If a minimum payment changes, a fee is added, or new purchases are made, the real result will differ from the estimate. That is why a calculator should be used as a planning tool, not as a guaranteed payoff schedule.
How to compare the methods
The Eerns Debt Snowball and Avalanche Calculator estimates payoff time, interest, and payoff order. This makes the tradeoff visible. If avalanche saves only a small amount but snowball feels easier to follow, the behavioral benefit may matter. If avalanche saves a large amount, the interest savings may be harder to ignore.
The cleanest way to use the calculator is to enter balances, APRs, minimum payments, and one extra monthly payment amount. Then compare the estimated payoff time and interest difference before choosing a strategy.