Problems start well above the 22%, 28%, or 35% figures people worry about. Most buyers we work with land between 38% and 45%, and a meaningful number are above that. When a ratio climbs well past 45%, the real constraint is usually income documentation rather than the appetite of the guidelines. One common upgrade mistake: calculating DTI from only the debts on your credit report and forgetting to add the new, larger housing payment. If you're at 22% today on existing debts and the move adds roughly a 20-percentage-point housing payment, you're really looking at 41% to 42%, which is still comfortable for a well-qualified borrower. The rough framework: - Under 45% with a 680-plus score is generally not a problem, with some flexibility beyond that. - Conventional: Fannie Mae caps DTI at 50% for loans approved through the automated system (DU). Manually underwritten conventional loans cap at 36%, stretchable to 45% with credit-score and reserve requirements. - FHA: automated approvals top out at 46.99% housing and 56.99% total. Those figures reflect how the TOTAL Scorecard behaves in practice (above them it tends to refer the file to manual underwriting) rather than a published HUD cap, and approval still depends on the AUS findings, compensating factors, and lender overlays. Stronger credit buys more room. The cleanest way to know is to run your current debts plus the projected new payment together, rather than looking at today's ratio alone.