CalcStack — free, instant, no signup. The interactive calculator loads automatically.
Two strategies, one winner — and the exact month you are free.
Every "snowball or avalanche" article argues philosophy. This calculator settles it with your actual debts: a month-by-month simulation of both strategies — minimums everywhere, your extra money aimed at the target, freed payments rolling forward — showing the payoff date and total interest for each, plus what your extra payment is worth versus minimums alone.
Anyone carrying multiple balances uses it to end the snowball-versus-avalanche argument with their own numbers — exact payoff dates and the dollar gap between strategies. The negative-amortization flag catches the trap most calculators never mention.
Avalanche (highest interest rate first) always wins mathematically. Snowball (smallest balance first) wins behaviorally — Northwestern researchers found the early quick win keeps people paying. The honest answer: run yours here. If the interest gap is a few hundred dollars, pick whichever you will actually finish; if it is thousands, find a way to love the avalanche.
On a typical three-debt pile ($23,000 across a card, medical bill, and car loan), $200 extra cuts roughly 20 months and $4,600 in interest versus minimums alone. The freed minimums rolling into the next target are the engine — the strategy compounds.
That is negative amortization — the balance grows even when you pay on time, and no strategy fixes it. Raise that payment above the interest first (the calculator flags this), call the issuer about hardship rates, or look at a lower-rate consolidation loan. Then run both strategies.
Consolidation helps when the new rate is clearly below your weighted average AND you do not run the cards back up — the second part is where it usually fails. Run your debts here first; if the avalanche finishes in under 3 years, the discipline path often beats the new loan.