THE NUMORIX GUIDE
How to use the Debt Payoff Calculator
Last reviewed September 14, 2026
What this calculator does
The schedule first sorts debts by descending APR, which is a debt-avalanche order.
Formula and method
The schedule first sorts debts by descending APR, which is a debt-avalanche order. Each month it applies minimum payments and then directs remaining extra monthly, annual, and one-time budget to the highest-rate unpaid debt. If fixedTotalPayment is true, a minimum payment freed when a debt closes is added to the remaining budget for later debts.
Variables and inputs
Each debt has a name, balance, monthly minimum payment, and APR. The plan also accepts extra monthly, extra yearly, and extra one-time payment amounts, the month for the one-time payment, and whether the total payment should stay fixed as debts are retired.
Worked example
With a $5,000 card at 20%, a $15,000 car loan at 5%, and a $25,000 student loan at 6%, first-month interest is $83.33, $62.50, and $125.00 respectively. After minimums of $100, $350, and $280, the balances are about $4,983.33, $14,712.50, and $24,845.00; a $200 extra budget then targets the 20% card first.
How to interpret the result
The result reports time to clear all debts, total paid, total interest, and the payoff order. Avalanche prioritization can reduce interest when rates are accurate, but a plan must also fit cash flow and preserve required minimum payments.
Common mistakes to avoid
Enter APR as a percentage, not a monthly rate. Keep each minimum payment attached to the correct balance. Do not put a yearly bonus in extra monthly or assume a freed payment is reused when fixedTotalPayment is off.
Assumptions and limitations
The engine assumes fixed balances apart from scheduled interest and payments, and it stops after 600 months. It does not model fees, promotional APRs, changing minimums, credit-score effects, collections, taxes, or the behavioral advantages of a snowball strategy.