There are a number of factors that go into estimating how much your regular mortgage payments will be. The most important numbers are the total mortgage amount (the price of the home, less the down payment, plus mortgage insurance if applicable), the amortization period (the number of months the mortgage payments will be spread across), and the mortgage rate (the rate of interest paid on the mortgage).
To use the calculator, enter the purchase price, and select your amortization period (in months) and mortgage interest rate. Then you can see your monthly rate, frequency of payments and the corresponding amortization schedule.