Finance
Debt Payoff Calculator
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Good to know
The minimum-payment trap
Card minimums are engineered near interest levels. Paying them feels responsible while the balance barely moves; this calculator exists to make that dynamic visible before it costs you years.
Snowball or avalanche?
When juggling several debts, avalanche (highest rate first) minimizes interest mathematically; snowball (smallest balance first) maximizes motivational wins. The best method is whichever you will stick to.
How it's calculated
The math behind this calculator
n = −log(1 − r·B/PMT) / log(1 + r)Each month, interest of B·r accrues; the payment covers it and attacks the balance. The closed-form solution above gives the payoff month count, and we simulate the schedule to capture the smaller final payment exactly. If your payment cannot cover the monthly interest, the balance grows forever; the calculator says so instead of pretending.
Assumptions & limitations
- Fixed payment and APR, no new spending on the account.
- Minimum-payment warnings: card minimums (~2–3% of balance) stretch payoff for decades.
- Simulated up to 100 years; balances needing longer report as unsustainable.
Worked example
An $8,000 credit card balance at 22.9% APR paid at $300/month clears in 38 months with $3,285.62 of total interest. Dropping to the interest-only level means never paying it off.
FAQ
Frequently asked questions
- Why did it say my payment never pays off the debt?
- Because the payment is at or below the monthly interest charge. Raise the payment above interest accruing, or negotiate the rate.
- Can I model multiple debts?
- Run each debt separately. To prioritize, order them by interest rate (avalanche) or balance (snowball) and roll cleared payments into the next.
- Does it assume I stop using the card?
- Yes; new purchases break the fixed-payment assumption entirely.
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