Enter up to 20 debts — names, balances, minimums, and rates — plus any extra monthly, yearly, or one-time payments. The calculator uses the debt avalanche method (highest APR first) and returns the payoff time, total interest, a principal-versus-interest split, and a per-debt payment schedule.
Avalanche vs snowball
| Method | Extra payment goes to | Typical result |
|---|---|---|
| Avalanche (this calculator) | Highest interest rate | Lowest total interest |
| Snowball | Smallest remaining balance | Faster “wins,” usually more interest |
Examples
Four debts · $100 extra a month
An auto loan ($25,000 at 4.9%, $519 minimum), a home mortgage ($250,000 at 4%, $1,800 minimum), Credit card 1 ($6,000 at 18.99%, $150 minimum), and Credit card 2 ($3,000 at 16.99%, $60 minimum), plus $100 extra each month with a fixed total, take 136 months (11 years and 4 months). The fixed monthly payment is $2,629. Total payments are about $356,853, of which about $72,853 is interest. Avalanche order is Credit card 1, then Credit card 2, then the auto loan, then the mortgage.
Same debts · $200 extra a month
The same four debts with $200 extra each month finish in 130 months (10 years and 10 months). The fixed monthly payment is $2,729. Total payments drop to about $352,358 and interest to about $68,358. Credit card 1 clears in 21 months, Credit card 2 in 27, the auto loan in 42, and the mortgage in 130.
Formula
Each month, interest is added to every remaining balance at the monthly rate, then payments are applied. Minimums are paid first; leftover extra goes to the highest APR, and leftover from a debt that is paid off in that month cascades to the next-highest rate.
monthly rate r = APR / 12 / 100
interest this month = balance × r
new balance = balance + interest − payment
With several debts the payment on each one changes whenever a higher-APR balance is retired, so the calculator walks month by month instead of using a single closed form.
The highest-rate-first ordering reduces modeled interest when rates stay fixed, there are no new charges or penalties, and the same total budget is maintained. Confirm that extra payments are applied as expected by each creditor.
Model boundaries
The schedule uses one fixed APR and minimum input per debt, adds interest monthly, and excludes fees, promotional-rate expirations, delinquency, prepayment charges, tax effects, and new borrowing. A payment that does not exceed monthly interest cannot amortize that balance. Use current statements and compare the result with creditor payoff information.