Debt Payoff Calculator
Plan debt payoff with snowball or avalanche strategy; add multiple debts and an extra monthly payment.
Written by Golam Rabbani, Founder & Lead Engineer
How to use this debt payoff calculator
- Choose a strategy: Avalanche (highest APR first) saves the most interest; Snowball (smallest balance first) builds momentum.
- Enter how much extra you can pay each month above the combined minimums.
- Add each debt: name, current balance, APR, and minimum payment.
- Click "+ Add another debt" to add more lines (up to 10).
- Press Calculate to see the total months to payoff, total interest paid, and per-debt timeline.
About this debt payoff calculator
A debt payoff calculator simulates how multiple debts get cleared month-by-month under two classic strategies: snowball (target the smallest balance first) and avalanche (target the highest-APR debt first). Mathematically, each month for each debt: new_balance = old_balance × (1 + APR/12) − payment, where payment = minimum (applied to every debt) plus extra (applied only to the strategy's current target). The simulation continues until every balance hits zero, accumulating the total interest paid (= sum across all months of old_balance × APR/12).
For example, with two debts — Card A at $5,000 / 22% APR / $100 minimum, and Card B at $3,000 / 18% APR / $80 minimum — plus $200 extra per month, the avalanche method (target Card A first) clears both in roughly 21 months with about $1,250 in total interest, while the snowball method (target Card B first) clears them in roughly 22 months with about $1,310 in total interest. Avalanche is mathematically cheaper; snowball is psychologically easier because you eliminate accounts faster. The U.S. Consumer Financial Protection Bureau's "Get out of debt" guides explain both at consumerfinance.gov/about-us/blog/get-out-of-debt-faster.
This tool is for estimation only and is not financial advice — for serious debt, consult a qualified financial advisor or a non-profit credit counsellor (in the U.S., look for an NFCC-accredited agency).
FAQ
- Which strategy is best — snowball or avalanche?
- Avalanche minimizes total interest because it targets the highest-APR debt. Snowball clears small debts faster, which can be motivating. If you will stick with the plan, avalanche is mathematically optimal; if you need quick wins to stay on track, snowball wins in practice.
- What if my minimum payment is less than the monthly interest?
- Then the balance grows each month and the debt is "minimum-trapped". The simulator will either take very long to converge or stop after 600 months with an error. Increase the minimum or extra payment until the balance falls each month.
- How is interest accrued?
- Each month every debt accrues balance × (APR ÷ 12) as interest before any payment is applied. This matches the way credit cards and most installment loans compute interest in the U.S.
- Are credit card fees and late fees modelled?
- No — only interest. Any annual fees, late fees, or balance-transfer fees should be added to the balance before you enter it.
- What happens when one debt is cleared?
- Its minimum payment is no longer needed, and the simulator continues paying minimums on the remaining debts plus the extra. (This is the "debt avalanche/snowball" cascade — the freed-up minimum rolls into the next target.)
- Should I use this for an actual payoff plan?
- Use it for estimation only. Real-world numbers vary by lender, billing cycle, and fees. For a binding plan, consult a qualified financial advisor or a non-profit credit counsellor.