How Much House Can You Actually Afford?

Debt-to-income ratio, or DTI, compares your monthly debt obligations to your gross monthly income. Front-end DTI looks only at your proposed housing payment; back-end DTI adds in every other recurring debt — car loans, student loans, minimum credit card payments — on top of housing. Most conventional lenders cap back-end DTI somewhere in the 43-50% range, and some government-backed loan programs allow even higher ceilings.

That ceiling represents the most debt a lender is willing to risk extending to you, underwritten against the chance you might default — it is explicitly not a recommendation for what leaves you financially comfortable. A lender doesn't know about your savings goals, your childcare costs, or how much you want to set aside for retirement. Their calculation happens once, at underwriting, using a formula that has nothing to do with your day-to-day budget.

A more conservative framework than the lender's maximum is the 28/36 rule: cap housing costs at 28% of gross income, and total debt at 36%. It's one of several commonly cited guidelines, not a regulation, and it doesn't account for your specific savings goals or other financial priorities. But it generally leaves substantially more monthly breathing room than a lender's 43-50% ceiling, which is exactly why it's worth running both numbers before deciding what to actually shop for.

The gap between what a 28/36 calculation suggests and what a lender's maximum DTI would approve is often $50,000-$100,000 of home price difference — a gap large enough that it's worth seeing explicitly rather than discovering after you're already under contract.

Someone with no other debt and modest day-to-day spending might genuinely be comfortable at a higher DTI than the conservative guideline suggests. Someone juggling student loans, a car payment, and aggressive retirement savings goals might find even the 28/36 guideline tight. The lender's approved number treats everyone the same; your actual budget doesn't work that way, and the only way to know which situation you're in is to look at your real numbers rather than trusting a single approved figure.

Two homes priced identically can have very different true monthly costs depending on the local property tax rate, HOA fees, and insurance costs specific to that home and area. A home affordability calculation that only looks at price without factoring in these recurring costs can point you toward a home that's technically affordable on paper but tight in practice once the full monthly bill arrives.

Consider a household earning $8,000 a month gross, with a $400 monthly car payment and $200 in minimum credit card payments — $600 in existing debt. At a lender's 45% back-end DTI ceiling, total debt payments (including housing) could reach $3,600 a month, leaving $3,000 available for a housing payment. At the more conservative 36% back-end DTI target, total debt caps at $2,880, leaving only $2,280 for housing — a gap of $720 a month between the lender's maximum and the conservative guideline, which over a 30-year mortgage translates into a meaningfully smaller loan amount and, often, a meaningfully less stressful monthly budget.

That $720-a-month gap is the entire point of running both numbers. It's the difference between a home that technically clears underwriting and a home that leaves room for savings, an emergency fund, and the unexpected costs that homeownership reliably brings.