This tool is used to compute the monthly principal, interest, taxes and insurance (PITI) payment and determine whether you qualify for a loan with your current level of income and debt. To compute, you must enter data for Annual Income, Sales Price, and Interest Rate. The other fields are optional. When all fields have been entered click the "Compute" button. To qualify, your Housing Expense Ratio must be 28% or less, and your Total Debt Ratio must be 36% or less.