Debt Payoff Calculator: Snowball vs. Avalanche

Both methods work the same way underneath: pay the minimum on every debt, then throw every spare dollar of your extra payment at exactly one target debt until it hits zero, then move that freed-up money to the next target. The only thing that differs is how the target is chosen. Snowball always picks the smallest remaining balance, regardless of its interest rate - so a $300 store card gets attacked before a $9,000 card even if the $9,000 card charges more interest. Avalanche always picks the highest interest rate, regardless of balance size - so a 27% store card gets attacked before a 6% car loan even if the car loan balance is much bigger. Avalanche is mathematically guaranteed to cost the same amount of interest or less than snowball for the exact same debts and extra payment; it can never cost more.

Run both in this calculator and look at the real numbers for your specific debts - that's the whole point of comparing them side by side rather than picking one on principle. If avalanche saves you a meaningful amount, that's real money worth taking. But debt payoff is a behavioral problem as much as a mathematical one: if past budgets have fallen apart from losing motivation, snowball's fast wins - crossing an entire account off your list in month two instead of month fourteen - keep some people paying consistently long after a 'smarter' plan would have quietly been abandoned. If the interest difference this calculator shows you is small, motivation probably matters more than the math. If it's large, that's worth weighing seriously before choosing based on feelings alone.

Every month, interest accrues first on every debt that still has a balance - the same order real statements use, so a debt sitting untouched for months still visibly grows here too. Then the minimum payment is applied to every open debt. Then your extra monthly amount, plus the minimum payments freed up by any debt that was fully paid off in an earlier month, gets applied to whichever single debt the chosen strategy currently targets. That target can change over time as debts get eliminated and the next-smallest-balance or next-highest-rate debt becomes the new target. This repeats until every balance reaches zero, or until 50 years pass - whichever comes first, with a clear warning if it's the second one.

This happens on some high-interest revolving debt where the required minimum is set low - often 1-3% of the balance - while the interest rate is 20% or more. In that case the minimum payment can be smaller than the interest charged that month, meaning the balance actually grows even while you're paying on time every month. This calculator checks every debt for exactly that condition and flags it with a warning if found. There are only two real fixes: get the minimum raised (some lenders will do this on request), or make sure some of your extra payment goes toward that specific debt from month one, since letting it sit on 'minimum only' can mean it never shrinks at all.

No - it assumes the APR you enter for each debt stays fixed for the entire simulation. That's accurate for most fixed-rate personal and auto loans, but if you're carrying a card with a variable rate, or a balance transfer with a promotional 0% period that reverts to a much higher rate after a set number of months, the real payoff will differ from what's shown once that rate changes. The practical fix is simple: re-run the calculator with the new rate as soon as it takes effect, and treat the result before that point as accurate only up to the change.

Because of how amortization works: on a high-APR balance, a large share of every minimum payment goes to interest first and only the remainder actually reduces the balance, so minimum-only payments can take years to make visible progress. Extra payment goes straight to principal with no interest deduction first, which is why even a modest extra amount - $50 or $100 a month - often cuts months or years off a payoff timeline and saves far more than that same amount would suggest at first glance. Try changing the extra payment field up and down in the calculator to see exactly how sensitive your own numbers are to it.

No. Every balance, rate and payment you enter stays in your browser - the simulation runs entirely in JavaScript on your device, and nothing is uploaded to a server at any point. You can safely enter your real numbers.

Yes - anything with a knowable current balance, interest rate and minimum payment works: car loans, personal loans, medical payment plans, store financing, even a loan from a family member if you're tracking it with a rate and a minimum. The one thing this tool isn't built for is a mortgage, since mortgages usually run 15-30 years with their own amortization schedule and are better handled by a dedicated mortgage calculator - but nothing stops you from adding one here if you want it included in the same combined plan.