For example, to calculate the monthly repayment of a $150,000 loan at 6.4% interest over 25 years, fill in the first three fields and click on "Compute" next to "Monthly repayment amount".
Then, to recalculate the term of the same loan with a higher monthly repayment, fill in the new value in "Monthly repayment amount" and click "Calculate" next to "Years of the loan".