An easy way to calculate mortgage payments is to use an online loan calculator tool, such as that offered by Bankrate. Enter the total amount borrowed, term of the loan and annual interest rate to get an estimate of the monthly mortgage payment amount.
Some online mortgage calculators offer additional information. For example, the mortgage calculator at Realtor.com shows a complete loan amortization, with estimates of interest and principal paid throughout the term of the loan, as well as a breakdown of monthly taxes and insurance costs.
Calculate a mortgage payment by hand by plugging the total loan amount, interest rate and number of months into the standard loan payment formula, as described by Finance Formulas.