How it works
Juggling several debts at once means making a choice that pure math tools ignore: which balance do you attack first? This calculator settles that question by running two strategies side by side on the same set of debts and showing the difference in both months-to-zero and total interest. You enter each debt's balance, its annual rate, and the monthly payment you'll direct at it; the tool iterates month by month, applying interest, subtracting your payment, and rolling any freed-up cash to the next debt in line.
The two strategies it compares are the snowball method (smallest balance first) and the avalanche method (highest interest rate first). Both assume you keep paying minimums on every debt while throwing extra at your target balance; once that one hits zero, its payment amount cascades onto the next target.
The formula
B_next = B × (1 + r/12) − P
Where B is the current balance, r is the annual interest rate (as a decimal), and P is the monthly payment. Each month the balance grows by one-twelfth of the annual rate, then shrinks by the payment. The calculator repeats this loop until B_next reaches zero, then moves the freed payment to the next debt in the chosen sequence.
Worked example
Suppose you carry three debts and can commit $600 per month total, allocated as shown:
| Debt | Balance | Rate (APR) | Minimum Payment |
|---|---|---|---|
| Credit card | $4,500 | 22.0% | $135 |
| Personal loan | $8,000 | 9.5% | $265 |
| Store card | $1,800 | 27.0% | $200 |
That leaves $600 − $135 − $265 − $200 = $0 extra, so to make a payoff strategy meaningful you add $200 of discretionary cash, bringing the total monthly pool to $800.
Snowball (smallest balance first): Store card → Credit card → Personal loan
Months 1–3: Pay minimums on the credit card ($135) and personal loan ($265), and put everything else—$800 − $135 − $265 = $400—on the store card. Its $1,800 balance at 27% retires in roughly 5 months.
Once the store card is gone, that $400 rolls onto the credit card. You now pay $135 + $400 = $535 monthly on the $4,500 balance at 22%, clearing it in about 10 more months.
Finally, $535 cascades onto the personal loan: $265 + $535 = $800 per month against the remaining $8,000 at 9.5%, finishing in roughly 11 more months.
Total: about 26 months, with roughly $2,780 in interest across all three debts.
Avalanche (highest rate first): Store card → Credit card → Personal loan
Here the order happens to match the snowball, because the store card also carries the highest rate. The payoff timeline and interest are nearly identical.
To show where the methods diverge, swap the credit card's rate to 24% so it outranks the store card by rate but still has the larger balance. Under the snowball you'd still clear the store card first; under the avalanche you'd hit the credit card first. The avalanche would then save roughly $310 in interest over the life of all three debts, because it kills the costliest balance earlier.
Things to watch
Minimum payments on some cards can drop as your balance falls, which changes the math slightly. This calculator assumes your monthly payment stays fixed at the amount you entered. It also assumes no new charges—if you keep using the cards, the payoff date keeps receding. And because rates, balances, and life circumstances shift, treat the result as an estimate rather than professional financial advice.