Debt Payoff Calculator
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Snowball vs. Avalanche: Paying Off Multiple Debts
When you're juggling several balances at once, the order you attack them in matters. This calculator simulates paying the minimum on every debt each month, then throwing all your extra money — plus the freed-up minimums from any debt you've already knocked out — at a single target debt, re-picking that target every month as balances change.
Snowball: Smallest Balance First
Targets whichever debt has the lowest remaining balance, regardless of interest rate. Quick wins build momentum and motivation, since you eliminate whole debts faster early on.
Avalanche: Highest Rate First
Targets whichever debt charges the highest APR, regardless of balance size. This is the mathematically optimal strategy — it minimizes total interest paid across all your debts combined.
Freed-Up Minimums Snowball Too
Once a debt is fully paid off, its minimum payment doesn't disappear — it gets rolled into the pool of money attacking your current target, accelerating every payoff after the first.
Which One Should You Pick?
Avalanche saves the most money mathematically, but snowball's early wins can matter more for staying motivated. Run both strategies here and see how big the difference actually is for your numbers.
Worked Example
Three debts — a $6,000 credit card at 24% APR ($150 minimum), a $1,500 store card at 18% APR ($50 minimum), and an $8,000 auto loan at 6% APR ($220 minimum) — with a $100 extra monthly payment:
- Both strategies: debt-free in 38 months.
- Snowball order: Store Card (month 11) → Credit Card (month 35) → Auto Loan (month 38). Total interest: $3,767.43.
- Avalanche order: Credit Card (month 34) → Store Card (month 35) → Auto Loan (month 38). Total interest: $3,594.93.
Same payoff date either way, but avalanche saves about $172.50 in interest by attacking the 24% card before the 18% card, since it's the highest-rate balance driving the most interest.
Snowball vs. Avalanche
- Snowball total interest: $3,767.43
- Avalanche total interest: $3,594.93
- Avalanche savings: ~$172.50
Why the Target Gets Re-Picked Every Month
As balances shrink, the "smallest balance" or "highest rate" debt can change — a debt that started second can become the new target once the original smallest balance is paid off. This calculator re-evaluates the target every single month rather than locking in an order upfront, which matches how the strategies actually play out in real life.
A note on this calculator: minimum payments are still made on every non-target debt each month, and the simulation caps at 600 months (50 years) — if your minimums and extra payment aren't enough to make progress within that window, the calculator flags it instead of looping forever.
Key Takeaways
- Avalanche Minimizes Interest: Mathematically, paying off the highest-APR debt first always saves the most money in total interest.
- Snowball Builds Momentum: Eliminating small balances quickly can keep you motivated, even if it costs a little more in interest.
- Freed Minimums Compound: Every debt you pay off speeds up the next one, since its minimum payment rolls into your attack fund.
- One Balance Instead? If you're only tracking a single credit card, our Credit Card Calculator gives a more focused single-balance view.