When a lender decides how much house you can afford, they don’t start with the listing price. They start with two percentages: 28 and 36. Known as the 28/36 rule, these two numbers are the lending industry’s classic shorthand for the debt-to-income (DTI) limits that separate an approvable mortgage from a declined one. Whether you’re buying your first home or your fifth, understanding these ratios — and where you stand against them — is the single most useful thing you can do before you talk to a lender.
What the two numbers mean
The rule has two halves, called the front-end ratio and the back-end ratio.
The front-end ratio caps your housing costs at 28% of your gross monthly income. Housing costs means the full PITI payment: principal and interest, property taxes, homeowner’s insurance, plus any HOA dues and mortgage insurance. Not just the loan payment — everything it costs to keep the roof.
The back-end ratio caps all your monthly debt payments at 36% of gross monthly income. That includes the housing payment plus car loans, student loans, credit-card minimums, personal loans, and child support. Lenders count minimum required debt payments — not rent, utilities, or groceries.
Both ratios use gross income (pre-tax), not take-home pay. That flatters affordability slightly, since taxes never appear in the ratio — which is why you should always sanity-check the lender’s ceiling against your actual take-home pay before falling in love with a listing.
Worked example: $120,000 household income
Take a household earning $120,000 per year, or $10,000 per month, with $800 per month in existing debt payments (a car loan and student loans).
- Front-end cap: $10,000 × 28% = $2,800/month maximum for all housing costs.
- Back-end cap: $10,000 × 36% = $3,600/month maximum for housing plus all debts.
- Housing budget after debts: $3,600 − $800 = $2,800/month for housing.
In this case both ratios agree: the household can spend up to $2,800 a month on housing. If the same household had $1,500 in monthly debts instead, the back-end ratio would bind first: $3,600 − $1,500 = $2,100, and the housing budget would shrink to $2,100 even though the front-end ratio still allows $2,800. The lower of the two results always wins — that is the whole point of having two ratios.
How lenders actually use it (and where they bend)
The 28/36 rule is the textbook version. In practice, different loan programs draw the lines in slightly different places:
- Conventional loans (Fannie Mae/Freddie Mac) commonly allow back-end ratios up to 43–45% with strong compensating factors — a high credit score, large cash reserves, or a big down payment.
- FHA loans are more generous still, often approving back-end ratios into the 50s for borrowers with solid credit and reserves.
- VA loans don’t publish a hard DTI cap at all, though lenders still scrutinize the borrower’s residual income.
Our Mortgage Affordability Calculator uses the conservative 36% back-end figure as its baseline, so treat its ceiling as a safe starting point rather than the absolute maximum a lender might offer. Being approved at 50% DTI and being comfortable at 50% DTI are very different things.
How to improve your ratios before you apply
You have three levers, and they work in this order of impact:
1. Pay down monthly debts. Eliminating a $400 car payment doesn’t just save $400 — at a 36% back-end ratio, it frees up $400 of monthly housing budget, which supports roughly $63,000 more in loan amount at 6.5% over 30 years. Small debts with big minimums are the highest-return payoff targets before a mortgage application.
2. Increase your down payment. A larger down payment shrinks the loan, which shrinks the payment, which improves the front-end ratio directly. It also helps you dodge private mortgage insurance, which counts inside the housing payment.
3. Raise your income — carefully. Lenders count stable, documented income: salary, steady bonuses, two-year histories of freelance or side income. A brand-new second job or a one-time windfall generally doesn’t count.
What doesn’t help: closing old credit cards (it can hurt your score), or shifting debt between cards. Lenders look at minimum payments and balances, not how cleverly the debt is arranged.
The 28/36 rule vs. real life
The ratios are guardrails, not a budget. A household at exactly 36% back-end DTI with high childcare costs, expensive health insurance, or lumpy freelance income will feel far more stretched than the ratio suggests — because none of those appear in the lender’s math. Financial planners often advise first-time buyers, single-income households, and anyone without a deep emergency fund to target housing under 25–28% of gross (or roughly 35% of take-home) rather than stretching to the maximum approval. The lender’s job is to measure default risk; your job is to measure your life.
What if you’re over the limits?
Failing the 28/36 test with a lender doesn’t mean homeownership is off the table — it means the current combination of price, down payment, and debt doesn’t work. You have five moves, roughly in order of effectiveness:
- Buy less house. The fastest fix. Every $10,000 off the price cuts roughly $64/month from a 6.5%/30-year payment — and it improves both ratios at once.
- Grow the down payment. Dropping from a $400,000 loan to $360,000 (10% down instead of 5% on the same price) cuts the payment by about $253/month and may eliminate PMI, which helps the front-end ratio twice.
- Kill a monthly debt entirely. Lenders count minimum payments, so eliminating one $300/month obligation frees $300 of back-end room — often more impactful than the same dollars added to a down payment.
- Add a co-borrower. A partner’s income counts (along with their debts and credit). Run the combined ratios before assuming it helps — a partner with heavy student loans can hurt more than their income helps.
- Wait and repair. Six months of aggressive debt payoff can move both ratios dramatically. A mortgage is a 30-year commitment; a 6-month delay to qualify cleanly is cheap insurance.
What not to do: stretch into an interest-only or adjustable product just to pass the ratios. Qualifying on a teaser payment you’ll never actually afford is how the 2008 crisis happened — the ratios exist to protect you, not just the lender.
DTI bands: where do you stand?
Not all DTI ratios are equal. Here’s how lenders generally read your back-end ratio:
- Under 28%: excellent — you’ll qualify for the best programs and have the most negotiating leverage.
- 28–36%: the comfort zone — standard approvals with good pricing across conventional, FHA, and VA.
- 36–43%: workable — conventional approval is common with compensating factors; expect more documentation.
- 43–50%: stretched — FHA territory or conventional with strong reserves and credit; pricing suffers.
- Over 50%: difficult — limited to specialized programs; most planners would call this overextended regardless of approval.
Compute yours now: add every monthly minimum debt payment (including the proposed housing payment), divide by gross monthly income. If you’re above 43%, treat debt reduction as step one of your homebuying plan — not an afterthought.
Key takeaways
- Spend no more than 28% of gross monthly income on total housing costs (front-end ratio).
- Keep all monthly debt payments, including housing, under 36% of gross income (back-end ratio).
- The lower of the two calculations sets your real budget.
- Conventional, FHA, and VA programs allow higher ratios — but approval is not the same as affordability.
- Paying off high-minimum debts before applying is the fastest way to raise your ceiling.
Frequently asked questions
Is the 28/36 rule a law?
No — it’s an industry guideline, not a statute. Individual lenders and loan programs set their own DTI caps, and many approve borrowers well above 36% back-end with compensating strengths. But 28/36 remains the benchmark underwriters are trained on, so it’s the right planning target.
Do lenders use gross or net income for DTI?
Gross — pre-tax income. This makes the ratios slightly more generous than they feel in take-home terms, which is why you should always cross-check the resulting payment against your actual budget.
What counts as a “debt” in the back-end ratio?
Minimum payments on installment and revolving debt: car loans, student loans, credit-card minimums, personal loans, child support, and alimony. Rent, utilities, insurance premiums, and groceries don’t count — though your budget must cover them.
Can I get a mortgage above a 43% back-end ratio?
Sometimes. FHA loans and some conventional programs approve higher ratios with strong compensating factors like excellent credit, large reserves, or residual income. Expect more documentation and scrutiny.
Does the 28/36 rule apply to refinances too?
Yes — lenders re-verify DTI on every mortgage application, including refinances. A refinance that looked easy at origination can get harder if your debts grew or your income fell since you bought.
How is DTI different from my credit score?
DTI measures cash-flow capacity (can you afford the payment?); the credit score measures repayment history (do you pay on time?). Lenders need both: a great score won’t fix a 60% DTI, and a low DTI won’t fix a 580 score.