Debt Payoff Calculator

Debt with multiple cards, loans, and balances at different rates feels like an impossible puzzle until you see the actual amortization side-by-side.

Enter your debts (balance, APR, minimum payment) and a monthly amount you can put toward debt, and the calculator runs both common strategies: avalanche (highest rate first) and snowball (smallest balance first). It shows total interest paid, payoff date, and a month-by-month schedule for each.

Mathematically, avalanche minimizes interest paid. Behaviorally, snowball is often better because closing small accounts produces visible wins that keep you motivated. The right choice is the strategy you'll actually stick to. The interest difference between the two is usually a few hundred dollars over a multi-year payoff — meaningful but not enormous.

The simulation runs month by month. Each month: every debt accrues interest at its monthly rate (APR ÷ 12), then minimums get paid on every debt, then any extra payment goes to the priority debt (highest rate for avalanche, lowest balance for snowball). When the priority debt hits zero, its minimum payment rolls into the next priority debt — that rolling effect is what makes both strategies accelerating. Continue until all debts are paid. Total interest is the sum of monthly interest charges across the entire simulation.

The pain this addresses: knowing intuitively that you should put extra money toward debt, but not knowing whether $200/month extra means paying off in 4 years or 7. The math is iterative — each month's balance depends on last month's, with cascading effects when a debt closes. Doing it on paper for one debt is fine; for five debts of varying rates and balances with rolling priorities, it's a half-day spreadsheet exercise. The calculator runs a 25-year simulation in milliseconds.

Worked example: $5,000 on Card A at 22% APR ($150 minimum), $3,000 on Card B at 18% APR ($75 minimum), $8,000 on Card C at 14% APR ($200 minimum), with $200/month extra to put toward debt. Avalanche (target Card A first) pays everything off in 39 months, total interest paid: $4,800. Snowball (target Card B first since it's smallest) pays off in 41 months, total interest: $5,100. Difference is $300 over 41 months. The avalanche wins on math; the snowball might win on follow-through if the early Card B closure keeps you motivated.

Where this can mislead: assuming the rates stay fixed. Variable APRs (most credit cards) can change with the prime rate. A balance starting at 18% can be at 22% in two years if the Fed raises rates aggressively. Your payoff date moves accordingly. Stress-test by running the simulation with rates 2-3 percentage points higher and see how much the timeline slips. If the answer is 'a lot,' that's a real risk worth pricing in to the decision.