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.
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.
Even a modest extra monthly amount above the minimums cuts interest sharply, because high-APR revolving balances compound every month. Paying extra on a low-rate mortgage is often less valuable than clearing credit cards first.
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.