DebtMath

Debt Avalanche Calculator

Pay off your highest-APR debt first, then roll its payment into the next. List every balance, APR, and minimum payment to see your debt-free date, total interest, and exactly how much the avalanche saves you vs. the snowball method.

Your debts

List each debt with its current balance, APR, and the minimum payment the lender requires. The avalanche method funnels everything extra into the highest-APR debt first.

Total monthly budget
$520.00
$420.00 minimums + $100.00 extra
Debt-free date
April 2030
3 years, 11 months
Total interest
$6,502.08
37.6% of starting balance
Total paid
$23,802.08
$17,300.00 principal + interest
Snowball vs avalanche: with these debts and this extra payment, both strategies finish at essentially the same time and cost. Pick whichever keeps you motivated.
Principal vs interest73% / 27%
Principal $17,300.00Interest $6,502.08

Payoff order

  1. 1
    Store card
    $1,800 @ 27.99% APR
    August 2027
    1 year, 3 months in
  2. 2
    Credit card
    $6,500 @ 23.99% APR
    November 2029
    3 years, 6 months in
  3. 3
    Personal loan
    $9,000 @ 11.50% APR
    April 2030
    3 years, 11 months in

Progress milestones

  • 25% paid offSeptember 2027 (1 year, 4 months in)
  • HalfwaySeptember 2028 (2 years, 4 months in)
  • 75% paid offJuly 2029 (3 years, 2 months in)

How avalanche differs from snowball

Both methods are debt-stackingstrategies: pay the minimum on every debt, then throw every extra dollar at one target debt until it's gone. When that debt clears, its minimum payment rolls onto the next target — the same fixed monthly budget now hits the new top of the stack even harder. The two strategies only disagree on which debt to target.

  • Avalanche: highest APR first. Mathematically optimal — minimizes total interest paid and (almost always) shortest payoff timeline.
  • Snowball: smallest balance first. Often clears your first account a few months earlier, which some people find motivating.

The cost gap depends entirely on your specific APRs and balances. A high-APR store card with a tiny balance is the rare case where both strategies pick the same debt. The more your APRs vary, the bigger the avalanche win — for a typical multi-card setup, avalanche commonly saves $500 to several thousand dollars over the full payoff period.

When does each strategy win?

Pick avalanche when:

  • Your APRs vary by more than a couple of percentage points (almost always true if you have any credit card debt).
  • You're comfortable with a longer wait before your first account closes — the math will catch up and overtake snowball.
  • Minimizing lifetime interest is your #1 goal.

Pick snowball when:

  • You've struggled to stay on a debt plan and need an early visible win to stay engaged.
  • Your APRs are clustered tightly — the dollar gap between avalanche and snowball is small.
  • One of your debts is small enough that you could clear it in one or two months and feel real progress.

The calculator above runs both simulations on your exact numbers and shows the gap in months and dollars, so you can make this call with the actual cost of motivation visible.

How the math works

The simulation marches forward one month at a time. Each month:

  1. Every active debt accrues interest at balance × (APR ÷ 12).
  2. Each debt receives at least its minimum payment from your total monthly budget (minimums + extra).
  3. Anything left over is applied to the active debt with the highest APR (ties broken by the order you entered them).
  4. Debts that hit zero are retired. Their freed-up minimum payment becomes part of next month's budget — the avalanche grows.

Unlike the closed-form n = −log(1 − i × P ÷ PMT) ÷ log(1 + i)formula used for single-debt calculators, multi-debt payoff requires simulation: each month's allocation depends on which debts are still active and which one currently holds the highest APR.

Frequently asked questions

What is the debt avalanche method?

The debt avalanche pays the minimum on every debt and funnels every extra dollar into the debt with the highest APR. Once that debt is gone, its minimum payment rolls into the new highest-APR debt — the payment going to your top-priority debt avalanches larger and larger each cycle. Because interest is the dollar cost of debt, attacking the highest rate first minimizes total interest paid.

Avalanche vs. snowball — which actually wins?

Avalanche almost always pays less total interest and finishes at least as fast, because it eliminates the most-expensive-per-dollar debt first. Snowball (smallest balance first) usually costs a bit more but delivers quicker early wins, which helps some people stay motivated. The calculator above runs both simulations and tells you the exact gap for your specific debts — sometimes it's hundreds of dollars, sometimes thousands.

When can snowball ever beat avalanche?

Rarely, and only when APRs are very close together (say, within a percentage point or two) and the smallest balance also happens to be one of the cheapest debts. In that case, snowball can clear an account a month or two earlier without giving up much interest savings. The comparison row in the results panel flags these cases automatically.

How is the monthly payment distributed?

Every active debt gets at least its minimum payment. Whatever's left of your total monthly budget (minimums + extra) goes to the highest-APR debt until it's paid off. After that, the freed-up minimum plus your extra rolls onto the next-highest-APR debt — that's the snowballing payment, just directed by APR rather than balance.

What if my minimum payments don't cover the interest?

The calculator will flag this as 'payment too low.' At minimums alone, those balances grow forever, so no strategy can pay them off. The fix is either a larger extra payment, a balance transfer to a lower APR, or negotiating a higher minimum that actually makes a dent. The avalanche math assumes your total monthly budget exceeds the total monthly interest accruing across all balances.

Does avalanche work for student loans and personal loans, not just cards?

Yes. The math is identical for any fixed-rate debt: rank by APR, pay the highest rate first. The one caveat is federal student loans, which sometimes have unique features (income-driven repayment, forgiveness, interest subsidies) that change the rate you should plug in. For consumer cards, personal loans, HELOCs in repayment, and most private student loans, avalanche is the rate to beat.

Related debt tools

Debt Snowball Calculator

Coming soon

Same multi-debt math, smallest balance first. Compare side by side.

Credit Card Payoff Calculator

Single-card payoff math — useful for a quick what-if on one balance.

Loan Payoff Date Calculator

When will any single fixed-rate loan be paid off?

Compound Interest Calculator

Same compounding math from the savings side.

Estimates are educational only. The simulation assumes fixed APRs, end-of-month payments, and that you don't add new debt during payoff. Real-world APR changes, late fees, and balance transfers will produce slightly different results.