Here's the confusing part about house hunting: you can afford more than you think, and also less. Both are true at once, depending on who's doing the math. The 28/36 rule is what a lender actually runs — before your credit score, before anything else — to sort out which one applies to you.
In one line: the 28/36 rule says spend no more than 28% of your gross monthly income on housing, and no more than 36% on all debt combined. Lenders use it to decide how big a mortgage you qualify for, and it's the fastest sanity check before you fall for a house you can't comfortably carry.
What the rule actually says
The 28/36 rule has two parts. The first: spend no more than 28 percent of your gross monthly income on housing costs — that's your mortgage payment, property taxes, insurance, and HOA fees if you have one, all added together. The second: spend no more than 36 percent of your gross monthly income on all debt combined — that includes the housing costs plus your car payment, student loans, credit cards, everything.
Gross income means before taxes. If you earn 60 thousand dollars a year, that's 5 thousand dollars a month gross, before the IRS takes its cut.
The caps at a glance
| Gross monthly income | 28% housing cap | 36% total-debt cap |
|---|---|---|
| $4,000 | $1,120 | $1,440 |
| $5,000 | $1,400 | $1,800 |
| $6,000 | $1,680 | $2,160 |
| $8,000 | $2,240 | $2,880 |
Read these as ceilings, not targets. Your real housing budget is whichever cap binds first — and once you subtract your existing debt from the 36-percent column, that's usually the one that wins.
Where it comes from and why it matters
Lenders didn't dream this up to make your life harder — they use it because it predicts default, plain and simple. Eat more than 28 percent of your income on housing alone and there's no cushion left for the day something breaks. Hit 36 percent on total debt and you're one job loss or one bad diagnosis from missing a payment. Not a guess: historically, people who cross those lines default more often, and lenders have decades of data to prove it.
So no, it's not a law. It's just a pattern that's held up long enough to become the industry default.
How to use it to figure out your number
Let's say you earn 5,000 dollars gross per month. The 28-percent test caps your housing costs at 1,400 dollars (28 percent of 5,000). The 36-percent test caps all your debt combined at 1,800 dollars (36 percent of 5,000). If you already pay a 300-dollar car payment and 200 dollars in student loans — 500 dollars in other debt — then subtracting that from the 1,800-dollar total-debt cap leaves 1,300 dollars for your mortgage payment, taxes, insurance, and HOA. The lower of the two caps is the one that binds, so your real housing budget here is 1,300 dollars, not 1,400. Want your own number? Run it through the home affordability calculator.
A 1,300-dollar housing budget typically means you can afford a house in the 250 to 300 thousand range, depending on interest rates and your down payment — the math is different in every market.
Here's a lever most people miss: because your other debt eats into the 36-percent cap, paying it down directly raises how much house you can afford. In the example above, clearing that $300 car payment drops your other debt to $200 — which lifts your housing budget from $1,300 back up to the full $1,400 the 28-percent cap allows. If you're house-shopping, knocking out a car loan or card first can do more for your budget than a bigger down payment.
The 28/36 rule isn't a permission slip. It's a warning light that tells you how much breathing room you actually have.
Why it's not the whole story
The rule assumes stable income and predictable expenses. If you're self-employed or your income varies, you might want to be more conservative. If you have a spouse whose income will stay stable even if one of you loses a job, you can sometimes stretch a bit. If you have dependents or aging parents you help support, or if your area has genuinely no affordable housing (most expensive markets), you might have to ignore this rule because ignoring it is the only way to get a roof over your head — that's a different problem.
The rule works best as a starting point, not as a ceiling.
The actual application
Use your 28/36 math to set your personal housing budget, then shop for houses in that range. When you get a pre-approval letter from a lender, the number they pre-approve you for will usually line up with or slightly exceed your 28 percent threshold — that's them running the same calculation. If the lender pre-approves you for way more, you can take it, but that doesn't mean you should. The 28/36 rule exists because people who stretch beyond it end up stressed.
Where this leaves you
The 28/36 rule is a lender's forecast of your stability — not a permission slip and not your true maximum. Use it to set a number you can actually live inside, not one you can technically survive for a couple of years until something inevitably breaks.
Frequently asked questions
What is the 28/36 rule? Housing costs shouldn't exceed 28% of your gross income, and total debt payments (including housing) shouldn't exceed 36%. Whichever cap is lower is the one that actually limits what you can borrow.
Why do lenders use the 28/36 rule? Historically, borrowers above those thresholds default more often — it's not a law, but a pattern that's held up well enough to become the industry default.