Debt Avalanche Payoff Calculator
The avalanche method pays minimums on everything and directs every spare dollar at the highest interest rate, then rolls that freed-up payment into the next highest. It is the mathematically optimal ordering, and this estimates what it costs you in months and interest.
How to use it
- Enter the balance, APR, and minimum payment for each debt.
- Enter any extra amount you can put toward debt each month.
- Read the months to payoff, total interest, and the priority order.
Why highest rate first is optimal
Interest accrues per dollar of balance at each debt own rate. A dollar moved from a 12 percent balance to a 24 percent balance saves twice as much interest per year. Since the total you pay each month is fixed, allocating the surplus to the highest rate minimises total interest by definition. Balance size does not enter into it.
A worked example: $8,000 at 22 percent and $12,000 at 9 percent, with $600 a month available. Avalanche clears the 22 percent balance first and finishes both in about 40 months with roughly $4,600 in interest. Attacking the larger 9 percent balance first takes about 44 months and roughly $5,900. Same money, same debts, $1,300 difference from ordering alone.
The rolling effect is what makes the back half fast. When the first debt clears, its minimum payment joins the surplus rather than being absorbed into spending. Each payoff accelerates the next, which is why progress feels slow for the first year and then compresses sharply.
Avalanche versus snowball
The snowball method targets the smallest balance first regardless of rate. It costs more in interest, and it is sometimes the better choice anyway.
The argument for it is behavioural. Clearing a small debt entirely produces a visible completed milestone, which sustains a plan that requires eighteen months of sustained discipline. A plan followed to completion at a $1,300 penalty beats an optimal plan abandoned in month seven, and abandonment is the common failure mode rather than a hypothetical one.
The practical resolution is to look at the spread. When rates differ sharply — a 24 percent card against a 6 percent loan — the avalanche advantage is large and worth the patience. When rates are similar, ordering barely matters and you should pick whichever you will actually stick to. It is also entirely reasonable to clear one small nuisance balance first for the momentum, then switch to strict avalanche.
Why minimum payments alone take so long
Credit card minimums are typically calculated as a small percentage of the balance, commonly 1 to 3 percent plus accrued interest, with a floor of around $25 or $35.
Because the minimum falls as the balance falls, the payoff curve flattens out and extends. On $5,000 at 22 percent with a 2 percent minimum, the first payment is about $100, of which roughly $92 is interest and $8 is principal. Paying only the minimum retires that balance in well over twenty years and costs several times the original amount.
This is the mechanism that makes any fixed extra payment so effective. A flat $150 a month on that same balance clears it in about four years. The extra amount goes entirely to principal, and unlike the minimum it does not shrink as the balance does.
What to check before starting
Two things can beat any ordering strategy outright. A balance transfer to a genuine zero-percent promotional rate stops interest accrual entirely for the promotional period, though the transfer fee of 3 to 5 percent and the rate that applies afterwards both need checking. Consolidating high-rate revolving debt into a lower fixed-rate instalment loan achieves something similar with a defined end date.
Also confirm whether extra payments are applied to principal. Some servicers default to holding an overpayment against the next scheduled payment, which does nothing for the balance. Where several balances sit with one servicer, extra amounts are often split proportionally rather than directed where you intended, which quietly defeats the whole strategy. It is worth one phone call to confirm.
At a glance
| Ordering | Highest APR first, minimums paid on the rest |
|---|---|
| Supports | Up to three debts plus an extra monthly amount |
| Assumes | No new charges and fixed rates |
| Transmitted | Nothing, balances stay in the page |
Frequently asked questions
Is avalanche always better than snowball?
Mathematically yes, but only by the interest difference. Where rates are similar, ordering barely matters, and a snowball plan you actually complete beats an avalanche plan you abandon.
Why do minimum payments take decades?
Because the minimum falls as the balance falls. On $5,000 at 22 percent, the first minimum is roughly $92 interest and $8 principal, so the balance barely moves.
Should I consolidate instead?
Possibly. A genuine zero-percent balance transfer or a lower fixed-rate instalment loan can beat any ordering strategy. Check the transfer fee and the rate that applies after the promotion.
Will my extra payment go to principal?
Not automatically. Some servicers apply overpayments to the next scheduled payment, or split them proportionally across balances. Confirm the handling with your servicer.
Read more
How loans actually work — Why your first payment is almost all interest, and why the term costs more than the rate.