Lenders don’t just look at how much they’re willing to lend you — they look at how much you can reasonably afford without stretching your budget to the breaking point. The most common shorthand for this is the 28/36 rule, and understanding it will tell you more about your real affordability than any pre-approval letter.

What the 28/36 Rule Actually Says

The rule has two parts:

  • 28%: Your monthly housing costs — principal, interest, property tax, and homeowners insurance (often abbreviated PITI) — shouldn’t exceed 28% of your gross monthly income.
  • 36%: Your total monthly debt, including the mortgage plus car loans, student loans, credit card minimums, and any other recurring debt, shouldn’t exceed 36% of your gross monthly income.

Gross income means before taxes — not your take-home pay. That distinction alone changes the math significantly for a lot of people.

Working Through the Numbers

Say your gross monthly income is $7,000.

  • 28% of $7,000 = $1,960 maximum for housing costs
  • 36% of $7,000 = $2,520 maximum for all debt combined

If you already have a $400 car payment and $150 in minimum credit card payments, that’s $550 already committed. Subtract that from $2,520, and your mortgage payment ceiling — after other debts — drops to $1,970, which happens to align closely with the 28% housing figure here. In many real cases, the 36% limit is the binding constraint, not the 28%.

Why Lenders Use Gross Income, and Why You Shouldn’t Always Trust the Max

Lenders qualify you based on gross income because that’s the industry standard, but your actual budget runs on take-home pay after taxes, retirement contributions, and health insurance. A payment that hits exactly 28% of gross income can easily eat 35-40% of your net income once those deductions are factored in.

This is the single biggest reason people feel “house poor” even though they qualified for the loan on paper.

A More Conservative Approach

Many financial planners suggest tightening the ratios to 25% for housing and 33% for total debt if you want breathing room for savings, emergencies, and irregular expenses like home maintenance. It’s a more conservative number than what a lender will approve you for, but it’s closer to what actually feels sustainable month to month.

Bottom Line

The 28/36 rule is a starting point, not a target. Use it to calculate a ceiling, then work backward from your actual take-home pay and existing obligations to find a number you’d be comfortable living with for the next 15-30 years — not just one that gets you approved.