Debt Payoff Calculator (Snowball vs Avalanche)

Getting out of debt is not just about paying more — it is about the order in which you attack your balances. The two proven strategies are the Debt Snowball and the Debt Avalanche. Both work, but they optimize for different things: motivation versus math.

This calculator simulates your exact situation month by month: it accrues interest on each balance (APR/12), applies your minimum payments, then rolls every spare dollar into your target debt. When a debt is paid off, its minimum payment snowballs into the next one — which is exactly why these strategies accelerate payoff.

How the Debt Snowball works

List every debt from smallest balance to largest, ignoring interest rates. Pay minimums on everything, then throw all extra money at the smallest balance. When it is gone, take the money you were paying on it (the minimum plus your extra) and attack the next smallest. Repeat until debt-free.

The power of the Snowball is behavioral: quick wins build momentum and adherence. Studies (e.g., Gal & McShane, 2012) show people are more likely to stick with a debt-payoff plan when they see accounts closed early.

How the Debt Avalanche works

Order debts from highest APR to lowest. Pay minimums on everything and direct all extra money to the highest-rate debt first. Once it is gone, cascade to the next highest rate.

The Avalanche is mathematically optimal: it minimizes total interest paid and usually finishes sooner. The trade-off is that if your highest-rate debt also has a large balance, the first 'win' can take longer to appear.

Which one should you choose?

• Choose Avalanche if you want to minimize interest and can stay motivated by the numbers.
• Choose Snowball if you need quick wins to stay consistent — the best plan is the one you actually follow.
• If your highest-rate debt is also small, both methods converge and the choice barely matters.
• The difference is often smaller than people expect: the real lever is the size of your extra payment, not the method.

The real variables that determine payoff speed

• Extra monthly payment: this is the single biggest accelerator.
• APR: high-rate credit-card debt (20%+) is a financial emergency; prioritize it.
• Minimum payments: if a minimum is below the monthly interest, the balance grows (negative amortization) — this calculator warns you about that.
• Lump-sum payments: any windfall (bonus, tax refund) applied to the target debt cuts months off the plan.
• Annual step-up: raising your extra payment each year as your income grows dramatically shortens the timeline.