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Loan Payoff Calculator

See exactly how many months it takes to pay off a debt at a fixed monthly payment.

Privacy: your files never leave your device. All processing happens locally in your browser.

How to use

  1. 1.Enter your current balance, the annual interest rate (APR), and the fixed amount you pay each month.
  2. 2.Read the payoff time in months (and the years-and-months breakdown) along with total interest and total paid.
  3. 3.Try raising the monthly payment or lowering the rate to see how much faster you become debt-free and how much interest you save.

About Loan Payoff Calculator

The loan payoff calculator answers a different question than a mortgage or car loan calculator. Instead of starting with a loan amount and a term to find your monthly payment, it starts with the payment you can actually afford and works backward to find how long the debt will last. That makes it ideal for credit cards, personal loans, student loans, medical debt, and any balance you're chipping away at with a fixed monthly amount. If you've ever wondered how many months of the same payment stand between you and a zero balance, this is the number it gives you.

You provide three inputs: your current balance, the annual interest rate (APR), and the fixed amount you pay each month. The calculator instantly returns the number of months to payoff (shown both as a whole-month count and as a years-and-months breakdown), the total interest you'll pay over that time, and the total amount paid. Everything runs locally in your browser, so your numbers never leave your device and there is no sign-up, upload, or wait.

The math is inverse amortization. Each month, interest accrues on the outstanding balance at a monthly rate equal to the APR divided by 12, and whatever is left of your payment after covering that interest reduces the principal. Rather than looping month by month, the calculator solves that recurrence directly for the number of periods, producing a closed-form answer that updates the instant you change an input. That precision is why two payments only a few dollars apart can still land on different payoff months.

One rule matters above all: your monthly payment must be larger than the first month's interest, otherwise the balance never shrinks and the debt can never be repaid. If you enter a payment that only covers the interest (or less), the tool tells you plainly that the payment is too low instead of showing a misleading or infinite number. This is exactly the trap that keeps people stuck in minimum-payment cycles for decades, quietly paying far more in interest than the original balance.

Use the calculator to compare scenarios side by side. See how adding fifty dollars a month can cut months, sometimes years, off your timeline, or how a lower APR from a balance transfer or refinance shrinks the total interest without changing your payment. Because the results are exact and immediate, it's a fast way to build intuition for how payment size and interest rate trade off against payoff speed, and to set a realistic target date for becoming debt-free.

A few assumptions keep the model clean: it uses a single fixed rate, the same payment every month, standard monthly compounding, and no new charges added to the balance. Real accounts can differ. Credit cards accrue interest daily, promotional rates expire, and lenders may apply fees or specific payment-timing rules. Treat the output as a solid planning baseline rather than an exact quote. Figures here are estimates for general information only and are not financial advice; confirm your exact payoff terms with your lender before making decisions.

Methodology & sources

Uses the inverse-amortization (annuity) formula n = -ln(1 - B·r/P) / ln(1 + r), where B is the current balance, P is the fixed monthly payment, and r = APR/100/12 is the monthly interest rate. When the rate is 0%, it simplifies to n = B/P. The model requires P > B·r (the payment must exceed the first month's interest); otherwise the balance never declines and the tool reports that the payment is too low. Total paid = P × n and total interest = total paid − B. Assumes a fixed rate, equal monthly payments, monthly compounding, and no additional charges. Estimates are for general information only and are not financial advice.

Frequently asked questions

How is this different from a mortgage or car loan calculator?
A mortgage or car loan calculator starts from a loan amount and term to compute your monthly payment. This tool does the inverse: it starts from the payment you already make and solves for how many months the balance will take to reach zero.
Why does it say my payment is too low to pay off the balance?
If your monthly payment is equal to or less than the first month's interest (balance times the monthly rate), the principal never decreases, so the debt can never be repaid. Increase the payment above that interest amount and a valid payoff time will appear.
Does the calculator account for extra charges or fees?
No. It assumes a fixed rate, the same payment every month, and no new charges added to the balance. Credit-card spending, late fees, or promotional-rate expirations will change your real payoff time, so treat the result as a clean baseline estimate.

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