Debt Payoff Calculator
How it works
Every debt is simulated one month at a time rather than solved with a formula, because the moment one debt is fully paid off, its minimum payment is freed up and gets redirected — a moving total no single equation captures cleanly. Each month, interest accrues on every debt still owed (balance · annualRate / 12), every debt's own minimum payment is applied, and then the extra monthly payment — plus the minimum payments of any debts already cleared — all goes to whichever debt is highest priority and still has a balance. Snowball ranks priority by smallest balance first; avalanche ranks it by highest interest rate first.
The simulation stops once every debt reaches zero, or after 1200 months (100 years) — past that point the minimum payments genuinely aren't covering the interest piling up, so the debt would never clear on its own.
Frequently asked questions
Snowball or avalanche — which should I pick?
Avalanche (highest interest rate first) minimizes the total interest you pay, full stop — it is the mathematically optimal order. Snowball (smallest balance first) usually costs a little more in interest, but clears a whole debt sooner, which is a real behavioral advantage: an early win is what keeps some people sticking with a payoff plan at all. Neither is "wrong" — pick avalanche if you are confident you will stay consistent either way, snowball if the early motivation matters more to you than shaving off some interest.
Why does the extra payment only go to one debt?
Both methods work by picking one debt at a time to focus on — the smallest balance for snowball, the highest rate for avalanche — and throwing every spare dollar at just that one, while every other debt keeps getting only its own minimum. Splitting the extra across several debts at once is a different (and slower) strategy: it waters down the very concentration that lets one debt disappear fast enough to free up its minimum payment for the next.
Does this assume minimum payments stay the same?
Yes — each debt's minimum payment is treated as constant for the life of the simulation. In reality many minimums are a percentage of the remaining balance, so they shrink as the balance does, which would stretch the true payoff time out a little longer than shown here. Treat the result as a best-case timeline assuming you keep paying at least today's minimum on every debt throughout.