Fastest/cheapest debt payoff plan. The Debt Payoff (Snowball/Avalanche) Calculator takes debt balance, interest rate, monthly payment, extra payment per month and returns months to pay off plus total interest at the current payment, months with the extra payment, interest saved with the extra payment. Results update as you type, and the formula is shown under the result so you can repeat it in your own spreadsheet.
The headline interest rate is only part of what a loan costs: fees, the structure of repayments and how the rate is quoted (flat or reducing) all change the true cost. Compare offers on total interest and effective rate, not on EMI alone. Use the worked example below to check the maths against your own figures.
How the Debt Payoff (Snowball/Avalanche) Calculator works
The payoff time depends on how much of each payment exceeds the interest. If the payment is less than the monthly interest the debt never clears; the calculator shows how a small extra payment shortens the term and cuts the interest.
Worked example
With the example values (debt balance of $200,000, interest rate of 18%, monthly payment of $8,000, extra payment per month of $2,000), the months to pay off is 2 years 8 months; total interest at the current payment $52,543.95, months with the extra payment 2 years, interest saved with the extra payment $12,981.71. Change any figure above and the result updates immediately; use Copy results to paste the summary into a note or email.
Assumptions and limits: If the payment does not cover the monthly interest the term shows as unavailable.
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Frequently Asked Questions
How is months to pay off calculated?
months = −ln(1 − balance × i ÷ payment) ÷ ln(1 + i), with i the monthly rate.
Which figures do I need?
Debt balance, interest rate, monthly payment, extra payment per month. Take them from the same period and the same set of accounts or reports so the ratio is consistent, and check the example values as a guide to the units expected.
Does the result include fees and charges?
Only where there is a fee input. Processing fees, insurance and prepayment charges add to the true cost; the APR and loan comparison calculators include them.
What assumptions does this calculator make?
If the payment does not cover the monthly interest the term shows as unavailable.
