Debt Snowball and Avalanche Payoff Calculator
Enter up to three debts with their balance, yearly interest rate and minimum payment, add any extra money you can spare, and pick a payoff order. Leave an unused debt at a balance of 0.
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Formula
Each month, for every debt with a balance:
- Add interest:
balance = balance × (1 + APR ÷ 12 ÷ 100) - Pay the minimum on every debt.
- Put all remaining money (the extra payment plus minimums freed by cleared debts) on the target debt. Avalanche picks the highest rate, snowball the smallest balance.
The monthly budget is the sum of the minimums plus the extra payment, and it stays constant. The calculator repeats until every balance is zero. Total interest is total paid minus the starting balances.
Worked example
Debts of 1,000 and 500, both at 0% interest, with minimums of 100 and 50 and an extra 50 a month:
- Budget is 100 + 50 + 50 = 200 a month
- 1,500 ÷ 200 = 7.5, so 8 months
- Interest is 0 and the total paid is 1,500
Comparing the two methods
With debt 1 = 8,000 at 22% (minimum 200), debt 2 = 5,000 at 9% (minimum 150) and 200 extra a month (budget 550):
- Avalanche targets the 22% debt: 29 months, interest 2,761.01, total paid 15,761.01
- Snowball targets the smaller 5,000 debt first: 30 months, interest 3,487.26, total paid 16,487.26
Frequently asked questions
What is the difference between the snowball and avalanche methods?
Both pay the minimum on every debt and put all spare money on one target debt. Avalanche targets the highest interest rate first and usually costs the least interest. Snowball targets the smallest balance first, which clears debts sooner and can be easier to stick with. With the default debts (8,000 at 22% and 5,000 at 9%, 200 extra) avalanche takes 29 months and 2,761.01 interest, snowball 30 months and 3,487.26.
What happens when one debt is paid off?
Its minimum payment is not spent elsewhere. It rolls into the next target debt, so the total paid each month stays the same until everything is cleared.
Can I check it with a simple example?
Yes. Debts of 1,000 and 500 at 0% interest, with minimums of 100 and 50 and 50 extra, give 200 a month in total. 1,500 ÷ 200 = 7.5, so the debts are cleared in 8 months with no interest.
Why does the calculator reject my numbers?
Each debt in use needs a minimum payment of at least 0.01, and the payments must be large enough to beat the interest.