Use this mortgage calculator application to determine how much house you can afford. By entering details about your income, down payment, and monthly debts, you can estimate the mortgage amount that works with your budget. Income, debts owed, and down payment amount are big factors when it comes to calculating your affordability, but there are other factors to be aware of. The interest rate you get could make a big difference in how much home you can afford. A lower interest rate could significantly lower your monthly mortgage payment. Your debts owed and spending habits also make an impact on your affordability.