When you're in the market for a new home, figuring out how much you can afford is essential. Instead of taking the time to go to the bank and find out how much a mortgage payment would be, you can instead use a mortgage payment calculator. These calculators are available online and can be used relatively quickly to determine how much you can afford.Using the CalculatorOnce you've located a mortgage payment calculator, you have to provide as much information as you know in order to get an accurate estimate. For example, most mortgage payment calculators will ask you for information such as the total mortgage amount and the interest rate. You will also be asked to enter in the term of the mortgage and possibly some other information.When using a mortgage payment calculator, you may not be sure what interest rate to enter. You cannot know for sure what kind of interest rate you can get until you get a quote from a mortgage lender. However, you can estimate what the mortgage rate will be by looking at market interest rates at the time of your calculation. Once you enter all of the information that the calculator asks for, you click the "Calculate" button or something similar, depending on the calculator you are using.Interpreting the ResultsOnce you have provided the appropriate information and calculated the payment, it is important to interpret what it actually represents. Most mortgage payment calculators provide you with only the principal and interest payment once you make a calculation.In reality, you usually can't get by just by paying a principal and interest payment. You'll still have to pay taxes and insurance on the property. Most mortgage lenders require you to make these payments each month as part of your mortgage payment into an escrow account. Then at the end of the year, the escrow agent pays your homeowners insurance and your property taxes on your behalf.Because of this discrepancy, it is important to factor in the extra costs for property taxes and insurance. Once you've made the proper calculations, you can get a realistic idea of what it will cost to buy a new home.