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Web Winder JavaScript Calculators: Missing Loan-Term Calculator


If you know any 3 of a loan's 4 terms (principal, interest rate, payments remaining, and payment amount), this calculator will help you to find the missing term. For example, if you know the interest rate, the payments remaining, and the payment amount, this calculator will compute the current payoff amount of the loan. All results should be interpreted as close approximations (testing to date has shown results to be accurate within .002% of the actual).

Instructions: Enter the 3 known loan terms in the appropriate entry fields and click on "Compute." Note that when trying to find the interest rate, please select a "guess" from the pull-down menu by the same name. The closer your guess is to the actual interest rate, the faster the calculator will arrive at a result. If you don't select a "guess" the calculator automatically starts out at a 10% guess and works up or down until it finds a close approximation. If it turns out the actual rate is 19.95% it could take the calculator as many 56,000 iterations to find the answer. On the other hand if you had "guessed" 19% the calculator's iterations will be reduced significantly.

Note: Other than decimal points, do not enter any other non-numeric characters (commas, dollar signs, percent signs, etc.) in the entry boxes. Doing so will cause a JavaScript error.

Principal (current payoff amount)

Interest Rate 
# of Payments Remaining
Payment Amount



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