Debt Payoff Calculator

Avalanche is always the mathematically cheaper route because it kills the most expensive interest first. Snowball clears the smallest balance first, which costs slightly more but delivers a visible win early — and the research on debt repayment consistently finds that people who see early progress are more likely to keep going. In practice the gap between the two is often modest, so the method you will actually stick with beats the one that is optimal on paper. Two things this model deliberately does not do: it assumes fixed interest rates and no new borrowing, and it keeps your minimum payments constant. Real credit-card minimums shrink as the balance falls, which stretches payoff much longer, so holding the payment steady reflects what you should do rather than what the lender will ask for.

Each month, interest is added to every balance at the monthly rate (annual rate ÷ 12), then all minimum payments are made. Everything left over — your extra payment plus the minimums freed up by debts already cleared — is thrown at one target debt: the smallest balance under snowball, the highest rate under avalanche. That growing attack payment is what gives the snowball its name.

The simulation assumes fixed interest rates, no new borrowing and payments made on time. It holds your minimum payment steady, whereas real credit-card minimums shrink as the balance falls. Fees, balance-transfer charges and promotional 0% periods are not modelled, so treat the payoff date as a clear estimate.

Four debts totalling 27,750 with 540 in minimum payments, plus 200 extra a month, clear in roughly 4 years under the snowball method — with the small store card gone within the first few months, which is the psychological win the method is built around.

1. List each debt on its own line: name, balance, interest rate, minimum payment.
2. Enter any extra amount you can put towards debt each month.
3. Choose the snowball or avalanche method.
4. Read your debt-free date and compare it with the alternative method shown.

• Letting the minimum payment fall as the balance drops instead of holding it steady.
• Adding new debt to a card you are actively paying off.
• Chasing the extra payment so hard there is nothing left for emergencies.
• Forgetting that promotional 0% rates end, often with the deferred interest applied.

The Debt Payoff Calculator simulates paying off all your debts month by month. Enter each balance, rate and minimum payment, add whatever extra you can afford, and it shows your debt-free date, total interest, the order debts get cleared and how the snowball and avalanche methods compare.

Anyone juggling several debts — credit cards, car loans, store cards or student loans — who wants a concrete payoff plan.

• Handles up to 25 debts at once, not just a single balance.
• Compares snowball and avalanche side by side, in months and in interest.
• Shows what minimum payments alone would cost you, so the extra payment has context.
• Charts the falling balance and exports the payoff order as CSV.

• Deciding whether to attack the smallest balance or the highest rate first.
• Working out how much sooner an extra 100 a month clears everything.
• Seeing the true lifetime cost of paying only the minimums.
• Setting a realistic, dated goal for becoming debt-free.