Debt Payoff Calculator: Avalanche vs. Snowball

How avalanche and snowball differ

Both methods have you pay the minimum on every debt, then throw all spare money at one target account. They disagree on which account.

Avalanche targets the highest interest rate first. It’s mathematically optimal — it always costs the least total interest. Snowball targets the smallest balance first, regardless of rate. It costs more, but it clears individual accounts sooner, and that visible progress helps some people keep going.

A worked example

Three cards: $3,000 at 24.99%, $1,500 at 18.99%, and $2,500 at 22.99% — $7,000 total, with $500 a month available.

Avalanche clears them in 17 months with about $1,155 in interest. Snowball also takes 17 months but costs about $1,304 — roughly $149 more.

That gap is smaller than most people expect, and it’s worth knowing why: when balances and rates are close together, the two methods pay off in a similar order anyway. The gap widens when you have one large high-rate balance sitting alongside several small low-rate ones. In that case avalanche can save hundreds more.

Choosing between them

If the difference is small — as it is above — pick the one you’ll actually stick with. A snowball you follow for 17 months beats an avalanche you quit in month four.

Choose avalanche when the rate spread is wide, when one balance is much larger than the rest, or when you’re confident you’ll stay the course. Choose snowball if past attempts have stalled and you need an early win. There’s also a middle path: clear one small balance first for momentum, then switch to avalanche for the rest.

Common mistakes people make paying off debt

• Adding new charges to the cards you’re paying down. This is what turns a 17-month plan into a permanent one.
• Paying only minimums. On a typical card, minimum-only payments can stretch a balance past a decade and cost more in interest than the original purchase.
• Draining the emergency fund entirely. Keep a small buffer. Without one, the next unexpected bill goes back on the card.
• Ignoring a balance-transfer option. A 0% introductory APR can beat either method outright — but check the transfer fee, usually 3-5%, and be certain you can clear it before the promotional rate ends.

What this calculator doesn’t account for

It assumes fixed interest rates, no new charges, and the same payment every month. Real cards have variable APRs, penalty rates if you miss a payment, and occasionally promotional periods. It also can’t weigh the psychological side, which is the entire reason snowball exists. Treat the interest figure as a solid estimate and the timeline as a best case that holds only if you stop adding to the balances.