How debt payoff calculators work

PaydownBase debt calculators simulate one month at a time: interest accrues on each open balance, minimum payments are applied, then any extra payment goes to the priority debt for your chosen strategy.

Monthly interest

For each debt, monthly interest is balance × (APR ÷ 12), rounded to cents. Principal paid in a month equals your payment minus that month's interest.

Snowball vs avalanche

Snowball sends extra payments to the smallest balance. Avalanche sends extra to the highest APR. Both keep paying minimums on every account until a balance hits zero, then roll freed payments forward.

What we do not model

Late fees, penalty APR resets, promotional 0% windows, and lender-specific payoff quotes are not included unless you enter them manually. See our methodology for Fed G.19 rate presets and known simplifications.

Try the debt payoff calculator or debt snowball calculator with the same debts and extra payment.