Debt Avalanche Calculator

Each month: pay every minimum, then send all extra to the highest-rate remaining debt. When it clears, its whole payment rolls onto the next-highest rate.

Why the avalanche is the optimal route

The debt avalanche goes straight after the most expensive debt — the one with the highest interest rate — regardless of its balance. You pay the minimum on everything, then throw every spare unit of money at the highest-rate debt until it is gone. When it clears, its whole payment rolls onto the next-highest rate, and so on. Because you are always killing the debt that is growing fastest, less interest accrues across the whole plan — which is why the avalanche always pays the least total interest, and usually reaches zero soonest too.

The calculator simulates this month by month, shows each balance vanishing highest-rate-first, and overlays the snowball’s total-balance curve so you can see the avalanche cross the finish line sooner and cheaper.

Worked example — three debts ($2,000 at 8%, $9,000 at 27%, $6,000 at 12%) with $350 extra a month: The avalanche attacks the $9,000 at 27% first — the costliest debt — even though it is not the smallest. That saves about $1,445 in interest and finishes two months sooner than the snowball, which would have cleared the $2,000 first.

Avalanche vs snowball — the honest comparison

The snowball targets the smallest balance first for a quick psychological win; the avalanche targets the highest rate first for the lowest cost. Mathematically the avalanche always wins on interest, and usually on time — but the margin depends on your debts. When your highest-rate debt is also large, the avalanche’s saving is substantial. When your debts have similar rates, the two methods nearly tie and the snowball’s motivational edge may be worth more than the small difference.

This calculator shows both side by side and the exact interest the avalanche saves, so the choice is informed rather than dogmatic. The one honest caveat: with the avalanche, your first cleared debt can arrive later than it would under the snowball, because you may be chipping at a large high-rate balance while a small one waits. If early wins keep you motivated, weigh that against the saving.

Accelerating the avalanche

Anything extra speeds the plan up. A one-time windfall — a bonus, refund or gift — applied to the current highest-rate target removes the most expensive principal first, so it saves the most interest of any prepayment. And stepping your payment up over time, as your income grows, compounds throughout the plan. Both are in the advanced options.

A note on scope: this tool assumes the fixed minimum payments you enter. Real credit cards often set the minimum as a percentage of the balance, which falls as the balance does — so on debts you are not yet targeting, a real minimum may drift slightly from the figure here. For the debt you are actively attacking, where you pay far above the minimum, the result is accurate.