Debt Payoff Calculator
Compare the snowball (smallest balance first) and avalanche (highest rate first) methods for paying off several debts at once with a fixed extra budget.
How to use this calculator
- 1List each debt as balance, interest rate, minimum payment — one per line.
- 2Enter how much extra you can put toward debt each month, beyond those minimums.
- 3Compare avalanche and snowball — the payoff order table shows exactly which debt clears first under your chosen strategy.
How the calculation works
Each month: pay every minimum, then apply (extra budget + freed-up minimums) to one target debt- target debt (avalanche)
- The remaining debt with the highest interest rate
- target debt (snowball)
- The remaining debt with the smallest balance
- freed-up minimums
- Once a debt reaches zero, its old minimum payment joins the extra budget for the rest
Avalanche minimises total interest paid, full stop — it always attacks the balance costing the most per dollar first.
Snowball can cost slightly more in interest but clears a full balance sooner, which is the whole point for people who need the visible win to stay motivated.
Worked example
$2,000 at 24% and $1,000 at 12%, $100 extra, avalanche
- 1.Avalanche targets the 24% balance first — every dollar of the $100 extra goes there each month while the 12% debt gets only its $40 minimum.
- 2.Once the 24% balance hits zero, its $60 minimum joins the pool, so the 12% debt then gets $100 + $60 = $160 a month instead of $40.
- 3.That acceleration clears both debts in 18 months for $449.27 total interest — versus 56 months and $1,485.36 in interest paying only the minimums, and $544.75 under snowball, which pays the smaller 12% balance first and leaves the 24% balance accruing interest for longer.
Result: Debt-free in 18 months, $449.27 total interest (avalanche) vs $544.75 (snowball) and $1,485.36 (minimums only)
What actually accelerates a payoff
Every debt is defined by three numbers: a balance, an interest rate, and a minimum payment. Paying only the minimum keeps a debt alive roughly as long as the lender designed it to last; any payment beyond that minimum goes straight to reducing the balance, which permanently stops interest from accruing on that portion for every remaining month of the debt. Because of that, paying down a high-rate debt early is effectively a guaranteed, risk-free return equal to that rate — a 24% credit card balance paid off a month early "returns" 24% annualized on that money, with no market risk attached, which is a bar few investments clear.
The debt snowball vs the debt avalanche
The two established strategies for attacking several debts at once differ only in which debt gets the extra money first — everything else about the mechanics is identical.
- Avalanche — targets the debt with the highest interest rate first, regardless of its balance. It minimizes total interest paid, mathematically, by always attacking whichever balance is costing the most per dollar.
- Snowball — targets the smallest balance first, regardless of its rate. It usually costs a little more in total interest than avalanche, but it clears a full account to zero faster — a visible, motivating win that behavioral research on debt payoff consistently associates with people sticking to the plan.
A step-by-step payoff process
Both strategies follow the identical mechanical process — this calculator's own simulation runs exactly these steps, month by month, until every balance reaches zero.
- 1List every debt — balance, interest rate and minimum payment for each one, in one place.
- 2Keep every minimum current — without exception — missing a minimum on any debt risks fees and credit damage that undermine the whole plan.
- 3Pick one target debt — using either avalanche (highest rate) or snowball (smallest balance), and send all extra money to that debt alone.
- 4Roll the freed-up payment forward — once the target debt reaches zero, its entire former payment — minimum plus whatever extra was hitting it — moves onto the next target debt, which now gets attacked even faster than the first.
- 5Repeat until every debt is gone — each payoff accelerates the next, which is exactly where both strategies get their name — the pool of money attacking the current target keeps growing.
Other levers besides the monthly payment
The payoff order is not the only variable that changes how fast debt clears.
- Negotiating a lower rate — a phone call to a credit card issuer, especially one backed by a solid payment history, sometimes secures a lower rate on an existing balance with no other changes required.
- A promotional balance transfer — moving a high-rate balance to a card with a temporary 0% introductory rate can pause interest accrual entirely for a limited window, though a transfer fee usually applies upfront.
- Consolidating into one lower-rate loan — replacing several debts with a single loan at a lower blended rate — worth comparing on total interest and term, not just the new monthly payment.
- Temporary extra income — directing any windfall or side income entirely at the current target debt, rather than splitting it, keeps the acceleration effect of either strategy intact.
- Not adding new charges — the entire plan assumes balances only go down — new spending on a card being paid off works directly against every month of progress already made.
What this assumes, and where it stops
Assumptions
- Interest compounds monthly at the flat annual rate entered for each debt — introductory or variable rates are not modelled.
- The full extra budget is available every month, with no gaps, and freed-up minimum payments are always rolled forward rather than spent elsewhere.
Limitations
- No new charges are modelled — this assumes you stop adding to these balances while paying them off.
- Doesn't account for promotional 0% periods, balance transfer fees, or a card's rate changing after an introductory period.
- A very large number of debts or an extremely small extra payment is capped at 100 years of simulation, after which the result would be unrealistic regardless of strategy.
Common questions
Is avalanche always better than snowball?
For total interest paid, yes — avalanche is mathematically optimal because it always attacks the most expensive balance first. Snowball can cost more in interest but clears a full account sooner, which behavioural research on debt payoff consistently finds keeps people going. The right choice depends on whether you need the momentum more than the last few dollars of savings.
What if I can't find any extra to put toward debt?
Enter $0. The calculator still rolls each freed-up minimum payment into the next target debt as balances clear, which pays off faster than the minimums-only baseline even without new money — it just takes longer than if you can add something extra from the start.
Why do the two strategies sometimes show almost the same result?
When your debts have similar rates, or the highest-rate debt and the smallest-balance debt happen to be the same account, avalanche and snowball converge on nearly identical payoff paths. The gap between them widens when a large, high-rate balance and a small, low-rate balance are different accounts.
Formula and content last reviewed on .
Results are estimates for information only, not professional advice.
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