This home mortgage payment calculator helps you determine how much your monthly mortgage payments may be. Loan amount, term, and interest rate are the major variables in this equation. Additional factors that may affect the outcome are the appraised value of the house, property taxes, and insurance costs. The amount of your down payment and the appraisal price of the property may determine if you require a monthly amount for private mortgage insurance (PMI). Mortgage lenders may require that you obtain mortgage insurance if your down payment is less than 20% of the home purchase price.