How the debt snowball works
Pay the minimum on every debt, then put every extra dollar on the smallest balance. When it is paid off, its minimum rolls into the next smallest, so the payment you aim at each debt keeps growing, like a snowball.
The calculator runs your debts month by month: each balance grows by its APR ÷ 12, the minimums are paid, and the rest of your monthly debt budget goes to the target debt.
Snowball vs avalanche
The avalanche targets the highest interest rate first instead of the smallest balance. It usually costs less interest; the snowball usually clears your first debt sooner, which keeps many people going. The calculator shows both side by side, so you can see what the quicker wins cost you, if anything.
What it leaves out
It assumes fixed APRs and minimum payments, no new charges, and payments on time. Many credit card minimums shrink as the balance falls; keeping your payment level, as the snowball does, is what makes it faster.
The formulas behind it
Every result cell is a plain spreadsheet formula, so you can check the math or rebuild it yourself.
| Cell | Result | Formula |
|---|---|---|
| B17 | Total debt | =B2+B5+B8+B11 |
| B18 | Paid toward debt each month | =B4+B7+B10+B13+B14 |
| B19 | Snowball: months to debt-free | Month-by-month schedule, smallest balance first |
| B20 | Snowball: total interest | Sum of each month’s balance × APR ÷ 12 |
| B21 | Avalanche: months to debt-free | Month-by-month schedule, highest APR first |
| B22 | Avalanche: total interest | Sum of each month’s balance × APR ÷ 12 |
| B23 | Minimums only: months | Each debt paid at its minimum, no extra |
| B24 | Minimums only: total interest | Same schedule without the snowball |
| B25 | Interest saved with the snowball | =B24-B20 |