These stylish Microsoft Excel calculator templates are easy to use, even if you're not an Excel expert, and they're perfect for business or personal use. Fill in the "Period" column.Fill in the column titled "Period" with your payment dates. This Excel spreadsheet makes it easy to view the amortization of a home loan with optional extra monthly payments. Enter your mortgage details here. Enter extra payment amount in relevant month rows. This Microsoft Excel template illustrates how to create a loan amortization schedule, as well as dealing with additional payments and variable interest rates. Now, you're ready to build your table to track payments. In your spreadsheet, set up columns to organize and calculate each payment's details. PMT (Payment Function): It calculates the fixed monthly payment for a loan based on the interest rate, loan term, and loan amount.