Calculate debt payoff

Compare highest-interest-first and smallest-balance-first payoff schedules under one fixed monthly debt budget.

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ToolDebt Payoff Calculator
Input
Output
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Preview

How it works

Each month adds one-twelfth of every annual rate, pays all minimums, then directs spare money to the highest-rate balance for avalanche or smallest opening balance for snowball. No statement values are assumed, and simulation stops after 1,200 months rather than presenting the safety ceiling as a payoff date.

Formula
monthly interest = current balance × annual rate ÷ 12
spare payment = monthly budget − sum of minimum payments
  • Avalanche minimises interest under the model, while snowball exposes the motivational tradeoff of clearing a small account sooner.
  • Balances below one cent are treated as paid after the final fractional calculation.

Worked example

Two cards and a loan
Each line is balance, rate and minimum payment
Input
											Debts: ["2000 19.9 50","5000 6.5 100","800 24.9 25"]
Monthly budget: 400
Output
												Avalanche months: 22
Avalanche interest: 672.89
Snowball months: 22
Snowball interest: 672.89
Saving: 0
Total debt: 7800
Recommendation: Both methods cost about the same here, so pick whichever you will actually stick to.

When to use this

Credit-card payoff plans, debt-counselling worksheets, and household cash-flow reviews compare interest cost with the motivation of closing a small account first.

Edge cases

  • A budget below the sum of minimum payments is rejected before simulation.
  • A debt line with a negative balance, negative annual rate, negative minimum, or extra column is rejected as malformed.
  • A budget that cannot clear interest and principal within 1,200 months is rejected instead of reporting the safety cap as a payoff date.