The percentage arrived at by dividing your monthly shelter costs (principal, interest, property taxes, heating and half of condo fees) by your gross monthly income and multiplying by 100. This is used by all lenders as a yardstick by which to measure the ability of a borrower (or borrowers) to make mortgage payments. For example, most lenders require that this ratio be no more than 32% for a particular application, while others allow higher limits. This is also the maximum qualifying GDS for most default insurance applications.