Debt Avalanche vs Snowball Planner

Each month, it computes interest from your APR using a simple monthly conversion (APR ÷ 12 ÷ 100). Then it calculates each debt’s minimum payment using your selected rule (fixed minimum or min = max(fixed, % of balance)). After that, it applies your Avalanche or Snowball extra payment to the “priority” debt (lowest APR for Avalanche; smallest balance for Snowball) while paying minimums on the rest.

Minimum payment rules matter a lot: a “min = max(fixed, % of balance)” model can automatically increase payments as balances decline, which changes both interest and payoff timing. The simulation updates only at month boundaries and assumes APR stays constant—no promotions, new charges, or fees. If your minimums are very high relative to your balances, the payoff schedule can compress and the interest savings between strategies may narrow.

If one balance starts at 0, the calculator effectively ignores that debt and reallocates payoff to the remaining one. If monthly extra is 0, both strategies still differ because the priority debt changes, but the impact is often smaller. If your inputs make it impossible to cover required minimums (especially in the first month), the calculator will flag the strategy as not feasible rather than producing misleading dates.

Make sure your minimum payments and APRs are entered per debt (not combined), and verify the units: APR is a percent per year, not a monthly rate. Don’t assume minimums are negotiable—this tool treats them as hard constraints and will not “skip” minimums to force a desired payoff date. If you’re trying to model a balance transfer or a rate drop, you’ll need a different APR setup; this planner assumes rates are steady.