The 28/36 Rule Explained: The Standard That Decides Your Mortgage Limit
The 28/36 rule: how lenders cap housing and total debt at 28% and 36% of gross income, with a worked example and the limits lenders will actually stretch to.
By The RateFig Editorial Team · July 30, 2026 · reviewed against official mortgage and rate sources
The 28/36 rule is the oldest shorthand lenders use to size a mortgage you can actually carry. It sets two ceilings as a percentage of your gross monthly income (before taxes):
- Front-end ratio: housing payment ≤ 28% of gross income.
- Back-end ratio: total debt payments ≤ 36% of gross income.
"Housing payment" here means PITI — principal, interest, taxes, and insurance — not just principal and interest.
A Worked Example
Household gross income: $8,000/month.
| Limit | Calculation | Ceiling | |-------|-------------|---------| | Housing (28%) | $8,000 × 0.28 | $2,240/mo | | Total debt (36%) | $8,000 × 0.36 | $2,880/mo |
Suppose existing debts (car loan, student loan, minimum cards) total $600/month.
- Housing ceiling from the back-end test: $2,880 − $600 = $2,280/mo.
- Housing ceiling from the front-end test: $2,240/mo.
The stricter of the two wins, so your housing payment should stay at or below $2,240/month. If taxes and insurance run $500/month, that leaves about $1,740 for principal and interest — which at a 6.5% 30-year rate supports a loan near $275,000.
Why the Ratios Exist
A payment that eats too much of your income leaves no cushion for repairs, job loss, or rate changes (on an ARM). The ratios are a rough risk model: borrowers who stay inside them default less. They are also a consumer-protection heuristic — a limit on how much house the math says you can stomach, not just what a lender will approve.
Where Lenders Actually Stretch
The 28/36 rule is a guideline, not law. In practice:
- Qualified mortgages can go to a 43% back-end ratio.
- With strong credit, reserves, or a large down payment, lenders sometimes approve 45–50% back-end.
- Government loans (FHA, VA, USDA) use their own calculators that can exceed 36% with compensating factors.
Approval above 36% does not mean it is comfortable. Every point past the guideline trades breathing room for buying power.
28/36 vs Your Real Budget
The lender's ceiling is the maximum, not the goal. A "budget rule" such as keeping housing under 25% or total debt under 30% often leaves more room for saving and life. That is why the amount you are approved for can exceed the amount you should borrow by a wide margin — the gap the 28/36 rule helps you see.
The Practical Check
List gross monthly income and every recurring debt payment. Apply 28% and 36%, take the lower housing ceiling, then subtract taxes and insurance to find the principal-and-interest you can support. Compare that to what a payment calculator says for your target price. If the price only works above 36%, you are leaning on the lender's outer limit, not your own cushion.
All calculations are approximate for planning purposes only. This article does not provide official financial, legal, or tax advice. Verify any decision with a qualified mortgage lender or financial advisor.
Frequently Asked Questions
What is the 28/36 rule in plain terms?+
It says your housing payment should stay at or under 28 percent of gross monthly income, and your total debt payments (housing plus everything else) at or under 36 percent.
Is 28/36 a hard limit?+
No. It is a traditional guideline. Many lenders approve above it — commonly up to a 43 percent back-end ratio for qualified mortgages, and sometimes higher with strong compensating factors — but the payment gets harder to carry.
Which matters more, the 28 or the 36?+
The 36 percent back-end ratio usually binds first, because it includes car loans, student loans, and cards. You can pass the housing test and still fail the total-debt test.
Where can I test my own numbers?+
Use the free affordability calculator at /tools/affordability-calculator/. It runs the same US-standard formulas in real time, no signup required.
Run the Numbers Yourself
Reading is the first step. The next is plugging your own numbers into a calculator that runs the same US-standard formulas in real time — no signup, no paywall, instant results.
Open the calculator→Key Takeaways
Use the calculator linked above to confirm how these concepts apply to your specific loan amount, rate, and term. Small changes in any one input can shift your monthly payment and total interest by thousands of dollars over the life of the loan.