Debt Payoff Calculator
See how making an extra monthly payment cuts the time and interest to clear a debt.
Written by Rahman · Last reviewed
Quick answer
On an $8,000 balance at 19.99%, one month's interest is $133.27 while a 2% minimum payment is $160, so only $26.73 of it reaches the principal and the rest just services the interest. That is why minimums stretch a debt out for decades. Every unit paid above the minimum comes straight off the principal, removing not only that amount but all the future interest it would have generated.
Results are estimates for general guidance and are not financial, tax or legal advice. Except where a calculator names a currency, figures carry no currency of their own: put in pounds and you get pounds back, put in rupees and you get rupees. Figures depend on the assumptions you enter and on rates that change over time. Check current rates and speak to a qualified adviser before acting on them.
About the Debt Payoff Calculator
Paying more than the minimum on a debt is one of the most reliable ways to save money. Every extra amount goes straight to the principal, which reduces the balance that interest is charged on, accelerating the payoff and cutting total interest.
This calculator compares your current payment plan with one that includes an extra monthly amount, showing exactly how many months and how much interest the extra payment saves.
Each month: interest = balance × (APR ÷ 12), then balance = balance + interest − (payment + extra).
The calculator runs this month by month for both plans and compares the time and interest.
Avalanche or snowball
Two orderings dominate the advice, and they optimise for different things. Both assume you pay every minimum and direct any surplus at one target debt.
- Avalanche: target the highest APR first. This is mathematically optimal and always costs the least in total interest.
- Snowball: target the smallest balance first. It costs more, sometimes considerably, but clears individual debts sooner and produces visible wins early.
The gap between them is usually smaller than people assume, and the plan you actually finish beats the plan that is theoretically optimal. If several debts sit at similar rates, snowball costs almost nothing extra. If one card is at 25% and the rest are at 6%, avalanche is worth the discipline.
Why minimum payments are designed to last
Card minimums are commonly set at a small percentage of the balance (often 1% to 3%) or a fixed floor, whichever is greater. Because the minimum shrinks as the balance shrinks, the schedule stretches out by design: the balance approaches zero asymptotically rather than reaching it.
On an $8,000 balance at 19.99% APR, one month's interest is about $133. A minimum set at 2% of the balance is $160, so only around $27 of that payment reaches the principal and the other $133 services the interest. Clearing a balance on minimums alone takes decades and costs more in interest than the original sum. Paying a fixed amount instead of a shrinking percentage is the single change that breaks the pattern, because the surplus over interest then grows every month rather than shrinking.
Frequently Asked Questions
Why does a small extra payment help so much?
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Extra payments reduce the principal directly. A smaller principal means less interest every following month, which compounds into large savings over the life of the debt.
Should I pay off debt or save first?
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Generally, clearing high-interest debt (such as credit cards) beats most savings returns. Keep a small emergency fund, then attack expensive debt aggressively.
What are the snowball and avalanche methods?
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With several debts, the avalanche method targets the highest interest rate first (cheapest overall), while the snowball method clears the smallest balance first (best for motivation).
Will extra payments always be allowed?
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Most loans allow extra payments, but a few charge prepayment penalties. Check your loan terms before committing to a strategy.
Sources
- 12 CFR § 1026.7(b)(12) — Regulation Z, periodic statement disclosures (eCFR) — Backs the section above on why percentage-based minimums stretch a balance out. Card issuers must print a bold minimum-payment warning, a repayment estimate at the minimum, and the payment that would instead clear the balance in 36 months. The regulation exists precisely because paying the minimum is so slow.
- 12 CFR § 1026.18(k) — Regulation Z, prepayment disclosure (eCFR) — Backs the FAQ answer on whether extra payments are always allowed. Subsection (k) requires a closed-end credit agreement to state whether a charge may be imposed for paying off principal early, which is why the loan document is the place to check before committing to an overpayment strategy.