Debt Avalanche Calculator
Target your highest-interest debt first to minimize interest. Compare avalanche vs snowball savings instantly.
A debt avalanche calculator simulates paying off multiple debts highest interest rate first: you make the minimum payment on every debt, direct all extra money to the debt with the highest APR, and when it is cleared, roll its freed-up minimum into the next-highest rate. The avalanche is the mathematically optimal payoff order — because every extra dollar always attacks the most expensive balance, no other ordering of the same budget pays less total interest, and it usually finishes soonest as well.
This tool runs the full month-by-month simulation on your actual debts and reports your debt-free date, total interest, and payoff order. It also runs the snowball method (smallest balance first) on the same debts, so you can see in dollars and months exactly what the avalanche's discipline earns over the more motivational alternative.
How it's calculated
Each simulated month applies three steps to every debt:
1. interest = balance × (APR ÷ 12) 2. pay minimums 3. extra + freed-up minimums → highest APR
Interest accrues monthly on each remaining balance, minimum payments are applied, and the entire leftover budget — your extra amount plus the minimums of every debt already cleared — goes to the highest-rate debt still standing. If that debt reaches zero mid-month, the remainder cascades immediately to the next-highest rate. The intuition for why this is optimal: a dollar of principal removed from a 24.99% balance stops about 25 cents of interest per year, while the same dollar on a 6.9% balance stops about 7 cents — the avalanche simply always buys the more expensive stop. Full formulas are on our methodology page.
Worked example: four debts, $25,500 total, $250 extra per month
Consider a debt set whose rate order differs from its balance order — that is where the avalanche earns its keep: an $8,000 credit card at 24.99% ($200 minimum), a $4,000 personal loan at 11% ($120), a $12,000 car loan at 6.9% ($260), and a $1,500 medical bill at 0% ($50). Minimums total $630; adding $250 extra makes the monthly budget $880. Computed with the same engine as the tool above:
| Strategy | Debt-free in | Total interest | First debt cleared | Payoff order |
|---|---|---|---|---|
| Avalanche | 41 mo (3 yr 5 mo) | $4,503 | Month 23 | Credit card → Personal → Medical → Car |
| Snowball | 45 mo (3 yr 9 mo) | $6,366 | Month 5 | Medical → Personal → Credit card → Car |
The avalanche saves $1,863 in interest and finishes 4 months sooner, because it kills the 24.99% card first while the snowball lets it compound for two extra years. The cost of that efficiency is patience: the avalanche's first cleared debt arrives at month 23, versus month 5 for the snowball — nearly two years without the psychological payoff of a zero balance. Note that the gap between methods is entirely scenario-dependent: when your smallest balance also carries your highest APR (as in this tool's seeded example), the two orders coincide and the results are identical. The wider the spread between your highest and lowest rates, and the larger the high-rate balance, the more the avalanche saves. Enter your own debts above to see the exact difference.
When should you use this calculator?
Use it to price the choice between payoff strategies on your actual debts rather than in the abstract — the side-by-side comparison shows whether the avalanche's advantage on your numbers is a few dollars or a few thousand, which is the fact that should drive the decision. It is also built for sizing the extra budget: in the example above, raising the extra from $250 to $500 cuts the avalanche timeline from 41 to 30 months and total interest from $4,503 to $3,076 — running your own increments shows what each additional monthly dollar buys. And mid-plan, re-entering current balances confirms whether the schedule still holds or a windfall should redirect the order.
The calculator answers the mechanical question: given these debts and this budget, what does each payoff order cost. Whether you will actually sustain a plan whose first win takes two years — and whether consolidation or hardship options fit your situation — are judgments the tool leaves to you.
Assumptions and limitations
- Interest compounds monthly at a fixed APR per debt. Credit cards actually accrue interest daily on the average balance; the monthly model is a close approximation.
- The extra budget is assumed constant every month until all debts are cleared, and freed-up minimums roll forward rather than being spent.
- Minimum payments are entered as fixed amounts. Real card minimums decline as the balance falls; the fixed-minimum model is slightly optimistic for cards.
- No new charges are modeled — fresh spending on a card mid-plan refills the balance and invalidates the schedule.
- Promotional 0% periods that later reset, deferred interest, and fees are not modeled; enter the rate you are actually paying, and re-run when a promo rate expires.
- Results are estimates for planning; lender day-count and rounding conventions shift figures slightly.
This page is educational content about how the debt avalanche method works mechanically. It is not financial advice and does not consider your personal circumstances. For decisions that matter, consult a qualified professional.
Last reviewed: 2026-07-09