What is DTI Ratio?

The Debt-to-Income (DTI) ratio is a primary credit underwriting metric that compares a borrower’s monthly recurring debt obligations to their gross monthly income (pre-tax earnings). Expressed as a percentage, the DTI ratio is utilized by mortgage underwriters to assess a borrower’s financial capacity to responsibly absorb a new mortgage payment without experiencing severe cash flow constraints. For underwriting purposes, the DTI is split into two distinct ratios: the front-end ratio and the back-end ratio.

The front-end DTI ratio, or housing ratio, measures the percentage of gross monthly income allocated solely to housing costs, including mortgage principal and interest, property taxes, homeowner's insurance, private mortgage insurance (PMI), and homeowners association (HOA) fees. The back-end DTI ratio is more comprehensive, calculating the percentage of gross income needed to cover all housing expenses plus other recurring monthly obligations, such as auto loans, student loans, minimum credit card payments, personal loans, child support, and alimony. While traditional guidelines favored a back-end DTI limit of 36% to 43%, modern Qualified Mortgage (QM) guidelines established by the Consumer Financial Protection Bureau (CFPB) have replaced the rigid 43% DTI cap under General QM rules with a price-based approach linked to the APR-to-APOR spread. Nonetheless, under federal Ability-to-Repay (ATR) regulations, lenders are still legally required to document, consider, and verify a borrower's debts and income before loan origination.