Part of our guide to How to Pay Off Debt Faster
The argument between avalanche and snowball is usually conducted with opinions. Your own numbers settle it in about thirty seconds.
What each method costs you on your actual debts — total interest, total paid, and time to clear. Avalanche always costs less; the useful output is how much less. When the gap is small, the easier method is the better one.
How the two methods work
Both do the same three things: pay every minimum, put all spare money against one debt, and roll that debt's minimum onto the next when it clears.
They differ only in which debt goes first.
Avalanche — highest interest rate first. Mathematically optimal, pays the least total interest, finishes soonest.
Snowball — smallest balance first. Costs slightly more, but the first debt disappears quickly, and that visible result is what keeps people going through the two or three years this usually takes.
The rolling is the engine. Each cleared debt frees its minimum, so the payment attacking your remaining debt grows every time one falls. That is why the last debt clears far faster than the first — the opposite of how it feels at the start.
How the calculation works
Simulated month by month rather than approximated, because the payment attacking each debt changes as debts clear:
- Interest is added to every outstanding balance
- Every minimum is paid
- Everything left over — your extra, plus the minimums of any cleared debts — hits the current target
Repeated until nothing remains. Ordering happens once at the start, since the target sequence does not change as balances fall.
The calculator runs this twice, once per method, on the same debts.
Reading the result
If avalanche saves a lot, use avalanche. The difference is money you keep.
If the gap is small, use snowball. This is the honest reading that most debt advice gets wrong: a method with a slightly worse theoretical outcome and a much higher completion rate is the better method. The best plan is the one you finish.
Try raising the extra. Because of the rolling, adding to the extra shortens the payoff more than proportionally.
What undoes the plan
Missing a minimum. Fees and penalty interest can erase months of progress, and the credit damage lasts years. Automate every minimum, then add the extra manually.
No buffer. The most common failure is not slow progress, it is progress that reverses — eight months of payments undone by one car repair that goes on a card. Build a small emergency fund first, then attack the debt.
Consolidating without changing anything. A loan that clears your cards leaves you with cleared cards. If the spending has not changed, within a year there are two debts.
Related tools and reading
- How to pay off debt faster
- Credit card payoff calculator
- How credit card interest is actually calculated
- Balance transfer cards — the maths
This is general information, not financial advice — see our disclaimer.
Frequently asked questions
What is the difference between avalanche and snowball?
Both pay every minimum and throw the extra at one debt. Avalanche targets the highest interest rate, which costs the least. Snowball targets the smallest balance, which clears a debt sooner and is easier to sustain.
Which one should I use?
If the gap in this calculator is large, use avalanche — the difference is real money. If it is small, use snowball, because a method you finish beats a better method you abandon.
Why does clearing one debt speed up the rest?
Its minimum payment does not disappear, it rolls onto the next debt. Each cleared debt makes the next one faster, which is why the last debt goes much quicker than the first.
Should I pay a little extra on everything instead?
No. Spreading extra money across four debts leaves all four accruing interest for nearly as long. Concentrating it clears one, and clearing one frees its minimum.
What if my payments never clear the balance?
If the minimums plus your extra come to less than the monthly interest, the total grows no matter how long you pay. The calculator says so and reports the figure you have to exceed.
Sources
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