Use the following formulas to show the total payment, interest portion of the payment, and principal portion of the payment. Microsoft Excel Mortgage Caculator XLS Worksheet.This calculator will help you figure out your regular loan payments and it will also create a detailed schedule of payments. The SIR value will be provided in the response file. This calculator will help you figure out your regular loan payments and it will also create a detailed schedule of payments. With our inputs converted into the right units, we're now ready to build our mortgage amortization table in Excel. There are three fields to fill in: home price, down payment and mortgage interest rate. In the dropdown box, choose your loan term. Enter the price of a home and down payment amount to calculate your estimated mortgage payment with an itemized breakdown and schedule. Use this calculator to find out how much money you might be able to borrow with a home equity loan and how much it might cost.