Calculate a Fixed Rate Mortgage (FRM) A fixed rate mortgage is a type of mortgage where the interest rate is fixed for the entire term of the loan. The interest rate is usually a bit higher than other types of mortgages but there's no way the interest rate can increase in the future. Principle Balance:    $ Interest rate of mortgage:      % Length of mortgage:      years Down Payment:    $ Starting month and year:     Jan Feb Mar Apr May June July Aug Sep Oct Nov Dec 2012201320142015201620172018201920202021 * Calculations do not include closing costs, insurance fees or taxes Definitions Principle Balance: The initial amount the mortgage is taken out for. Interest Rate: The cost of borrowing the money. Length of Mortgage: The number of years you have to pay the money back. Down Payment: Amount of money that you pay off when you take out the mortgage. This amount gets deducted from the principle balance and does not get charged interest. Starting Month and Year:     The month and year that the mortgage starts.