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FundlyCalc

Debt Payoff Calculator

Estimate how long it may take to pay off multiple debts under snowball versus avalanche ordering. Enter balances, APRs, minimum payments, and any additional monthly amount. Results are educational estimates — not credit counseling or financial advice.

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How this calculation works

Each month, interest accrues on remaining balances using monthly rate = APR ÷ 100 ÷ 12. A shared cash pool pays contractual minimums on active debts, then applies leftover cash (including your additional payment) to the strategy target.

Snowball targets the lowest balance first. Avalanche targets the highest APR first. Ties break by debt name ascending. After interest each month, order is recomputed on remaining balances.

When a debt is paid off, its minimum is no longer contributed to the pool in later months. Same-month leftover cash can waterfall to the next target.

Assumptions

  • Fixed APR and fixed minimum payment per debt for the simulation.
  • No new charges, fees, or penalty APRs.
  • Additional monthly payment is constant every month.
  • Debt names must be unique (case-insensitive).

Limitations

  • Does not model credit scores, hardship programs, or settlement offers.
  • If a minimum does not cover interest and there is no extra payment, payoff may be impossible under these assumptions.
  • Simulation stops after a safety cap of 1,200 months.

Frequently asked questions

Which strategy is better for me?
This tool does not recommend a strategy. It estimates timelines under both orderings from the same inputs so you can compare results yourself.
Does paying off a debt increase my extra payment?
The MVP uses a cash-pool model: each month the pool is rebuilt from minimums still due on active debts plus your additional amount. Freed minimums are not separately rolled into an “extra” bucket beyond that pool math.

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