There is a lot of advice about paying off debt and most of it is about motivation. The arithmetic is simpler than the advice, and once you can see it you can pick a method for your own reasons instead of someone else's.
The two orders
You have several debts. Each has a balance, a rate and a minimum payment. Every month you pay every minimum, and on top of that you have some extra amount to throw at the pile. The only question is: which debt gets the extra?
- Avalanche: the highest interest rate first. Mathematically optimal. It pays the least total interest and, in almost every case, finishes soonest.
- Snowball: the smallest balance first. It clears a debt sooner, which is a real psychological win, and the freed-up minimum then rolls onto the next debt.
The rolling minimum is the part people underestimate. When a debt clears, its minimum does not go back into your pocket; it joins the extra. So the pool aimed at the next target grows every time one is paid off, and the last debt always goes faster than the first, whichever order you chose.
A worked example
Three debts, $200 a month extra:
| Debt | Balance | APR | Minimum |
|---|---|---|---|
| Store card | $1,200 | 27.9% | $35 |
| Car loan | $9,800 | 6.4% | $310 |
| Credit card | $6,400 | 22.9% | $130 |
Avalanche goes store card → credit card → car loan. Snowball goes store card → credit card → car loan too, because the smallest balance also happens to carry the highest rate. That is common, and when it happens the two methods agree.
Change one number, a $3,000 medical bill at 0% with a $100 minimum, and they diverge. Snowball clears the medical bill first (smallest balance) while the 22.9% card keeps compounding; avalanche ignores the 0% debt until the end. On this pile the avalanche saves a few hundred dollars in interest and finishes a month or two earlier. On a bigger pile with a wider spread of rates the gap can be thousands.
That is the whole difference. Neither is wrong. Avalanche is cheaper; snowball gives you a paid-off account sooner, and if that is what keeps you paying the extra, it is worth the difference.
What the Debt page does
It walks the schedule month by month for both orders, always, so you never have to guess which one you should have picked.
- Every credit card and loan with a balance goes on. The rate and minimum come from the bank where the connection reports them (marked issuer), from what you typed (yours), or from a conservative estimate that exists so the page is never empty. Correct the estimates; a 0% "unknown" understates interest until you do.
- A mortgage is planned on principal and interest only. The payment your servicer reports usually includes escrow, which never pays down the loan.
- Skip leaves a debt out of the plan without excluding the account anywhere else: a 0% promotional balance on its own schedule, a loan someone else pays.
- Choose a method and an extra amount. The hero shows the debt-free month, what you are paying monthly, and the interest to pay over the whole plan with the saving against minimums-only. The instead tile shows the other method's date and interest under the same money, and the chart draws both curves.
- Switching the method or typing an extra recalculates at once without saving. Save plan keeps it for the household.
The walk is deliberately simple: one month of interest at APR ÷ 12, the minimum, then the pool to one target at a time. No daily compounding, no promotional periods that expire, no fees. It is arithmetic, not advice: the same balances, rates and payments always give the same date.
The number to actually watch
Not the method. The extra. Going from $0 to $200 a month extra changes the debt-free date by years on most piles; going from avalanche to snowball changes it by months. Pick whichever order you will stick to, then find the extra, then protect it. The cash timeline on Today is where you find it: it places every bill and paycheck on the next 60 days and shows what is left, so "$200 extra" is a number you can test against your actual month rather than a hope.
The page is in the left rail under Cash Flow, and the Debt guide has every rule the walk follows, including the ones this article simplified.