Front-End vs. Back-End DTI: What Each One Measures
Front-end DTI measures only housing costs (mortgage principal, interest, tax, and insurance) as a percentage of gross income. Back-end DTI measures all debt payments combined — housing plus every other recurring debt — as a percentage of gross income. Lenders typically check both, since a favorable housing-only ratio can still come with an unfavorable total-debt picture once other obligations are added.
Seeing two different DTI percentages referenced in the same lending conversation can be confusing until the distinction between the two is made explicit.
Front-end DTI
Front-end DTI isolates housing costs specifically — the new mortgage payment (principal, interest, tax, insurance, and any HOA dues) divided by gross monthly income. A commonly cited threshold is around 28%, though this varies by loan program.
Back-end DTI
Back-end DTI is the broader figure — housing costs plus every other recurring debt payment (car loans, student loans, credit card minimums) combined, divided by gross monthly income. This is generally the more commonly cited DTI figure in lending discussions, with a common threshold around 36–43%.
Why lenders check both
Someone with a very affordable housing payment relative to income but substantial other debt (student loans, a car payment) can have a comfortable front-end ratio alongside a concerning back-end ratio — checking only one figure would miss a meaningful part of their overall financial picture, which is why lenders generally evaluate both together.