Debt Avalanche Calculator
The debt avalanche method clears your highest-APR debt first to minimise total interest. List each debt with its balance, APR and minimum payment, add a shared extra payment (plus optional annual and one-time lump sums), and see the payoff order, your debt-free date, how much interest the avalanche saves versus paying minimums only, and how it stacks up against the debt snowball.
Formula
Worked example
Three debts: $8,000 at 24.9%, $5,000 at 18.5%, $12,000 at 6.5%, with minimums of $200, $120, $250 and a $300 extra payment. The avalanche pays minimums on all three and throws $200 + $300 = $500 at the 24.9% card first. When it clears, that $500 rolls onto the 18.5% debt, then the freed payment onto the 6.5% loan, clearing all three in about 35 months with roughly $4,988 in interest, saving about $9,268 and 52 months versus paying minimums only.
How the debt avalanche works
The avalanche method ranks every debt by its annual percentage rate (APR), from highest to lowest. Each month you pay the minimum on all of them, then direct one shared extra payment at the debt with the highest APR. The moment that debt is gone, its old minimum plus the extra rolls onto the next-highest-rate debt, then the next, growing the attack payment as you go. Because the most expensive interest is eliminated first, the avalanche mathematically minimises the total interest you pay across all your debts compared with any other payoff order.
How this calculator simulates your plan
This tool steps through your plan one month at a time. First it accrues interest on every open debt at its monthly rate (APR divided by 12). Then it pays each debt its minimum and pours the extra payment, plus any minimums freed by debts you have already cleared, into the highest-APR debt that remains. It repeats until every balance reaches zero, giving the exact months to debt-free, a debt-free date, and total interest. It also runs a minimum-only baseline and a debt snowball plan from the same numbers, so you can see precisely how much interest and time the avalanche saves you and how it compares with the snowball.
Extra, annual and one-time payments
The single most powerful lever is the extra monthly payment: every dollar above the minimums goes straight at the priciest debt and compounds your progress. Open the advanced options to add a recurring annual payment (handy for a yearly bonus or tax refund, applied every twelfth month) and a one-time lump sum dropped in whatever month you choose. The calculator folds all three into the same roll-down simulation, so the payoff date, interest total and savings always reflect your full plan. The balance chart shows the avalanche curve against paying minimums only, and the schedule lists the order your debts clear and roughly when.
Avalanche versus snowball
The debt snowball method instead targets the smallest balance first, regardless of rate, to win quick psychological victories. The avalanche always costs the same or less in total interest and usually less time, because it kills the priciest rate first; this calculator shows the exact interest gap between the two for your debts. The snowball can keep some people motivated with faster early wins. The gap is often modest, so the most important thing is choosing a consistent extra payment you can sustain. These figures are estimates: confirm your exact APRs, fees and minimum-payment rules with each lender before committing.
Avalanche vs snowball at a glance
| Feature | Debt avalanche | Debt snowball |
|---|---|---|
| Attack order | Highest APR first | Smallest balance first |
| Total interest | Lowest possible | Usually a little more |
| Time to debt-free | Usually fastest | Same or slightly longer |
| Early wins | Can be slower | Fast first payoff |
| Best for | Saving the most money | Staying motivated |
Both pay minimums on every debt and roll freed payments forward; they differ only in which debt gets the extra first.
Frequently asked questions
What is the debt avalanche method?
You pay the minimum on every debt, then put all spare money toward the debt with the highest APR. When it is paid off, you roll that whole payment onto the next-highest-rate debt, and so on. This order eliminates the most expensive interest first and minimises the total interest you pay.
Is the avalanche better than the snowball?
In pure dollars, yes: paying the highest-APR debt first always costs the same or less in total interest and usually clears your debts soonest. This calculator runs both and shows the interest gap. The snowball (smallest balance first) can be more motivating thanks to quicker wins, so pick the method you will actually stick with.
Can I add a bonus or tax refund to my plan?
Yes. Turn on the advanced options to add a recurring annual payment, applied every twelfth month, and a one-time lump sum dropped in the month you choose. Both are thrown at the top of the avalanche order, and the payoff date, interest and savings update to include them.
What if my plan never pays off?
If your combined payments do not out-pace the interest charged each month, balances grow instead of shrinking and no debt-free date appears. Increase the extra monthly payment, or raise a minimum, until the calculator shows a payoff time. The avalanche concentrates money on one debt, which helps it clear faster.