Debt payoff calculator: snowball vs avalanche

Enter up to four debts and one number for extra monthly payment. The calculator runs both classic payoff orders - snowball (smallest balance first) and avalanche (highest interest rate first) - and shows the time and total interest for each, so the trade-off stops being abstract.

Which order actually wins?

With fixed APRs, the same monthly budget and all minimums paid, avalanche directs the remaining money to the highest rate to minimize interest. Snowball prioritizes clearing smaller balances. Compare the modeled cost with the order you can consistently follow. Actual fees, changing rates and minimums can change the result.

Related reading

Start with which debt to pay off first for the reasoning in plain English, then the debt snowball method and the debt avalanche method for each system step by step. Weighing a consolidation loan instead? See does debt consolidation always save money.

The formula this calculator uses

monthly budget = sum of the starting minimums + extra payment
interest each month = opening balance * APR / 100 / 12
pay every debt's minimum first, capped at what it owes
apply the remaining budget in the chosen starting priority order:
  snowball: smallest starting balance, then higher APR
  avalanche: highest APR, then smaller starting balance
unused payoff money goes to the next debt in the same month
cleared minimums remain in the fixed monthly budget
the final payment is capped at the remaining amount owed

What it assumes without asking

• The calculator uses the positive minimum payments you enter without replacing them
• Minimums stay flat rather than falling with the balance
• No new borrowing on any of the accounts
• APRs hold steady for the whole payoff
• The fixed budget is paid every month until the debts are cleared
• Interest accrues before month-end payments, with full precision until display
• A plan exceeding 1,200 months is reported as unfinished, not as a payoff date

One worked example: three debts, $200 extra and a $501 monthly budget

What this calculator does not model

• Fees, penalty rates and any promotional period
• The chance that clearing a small balance early keeps you going, which is the actual argument for the snowball and is not a number
• Any change in income during the payoff

The guide behind this tool

A number on its own does not tell you what to do with it. The full month-by-month simulation of these exact debts, and what the two orders cost against each other, is in debt snowball against debt avalanche.

This tool is general education, not personalized financial advice. It assumes fixed rates and payments and ignores fees - real accounts vary. See our disclaimer.