What Percentage of Income Should Your Mortgage Be? (The Real Math)

It’s 11:43 PM. The house is quiet, save for the faint hum of the refrigerator, and you’re staring at an online property listing with a tab open to a mortgage calculator. You’ve crunched the numbers three times, but they keep shifting. On paper, the monthly payment looks doable—if you never buy a new pair of shoes, cancel your streaming services, and somehow never have an emergency trip to the dentist. But your stomach is doing that familiar, tight flip. You aren’t just wondering if a lender will approve you; you’re wondering if you’re about to trap yourself in a financial cage.

If you’ve typed what percentage of income should your mortgage be into a search engine tonight, take a slow breath. You are not the first person to feel the dizzying gap between what a bank says you can afford and what actually feels safe to pay. Lenders look at your life through a wide-angle lens that misses all the texture—the grocery bills, the aging car, the desire to save for a rainy day or take a real vacation.

Let’s strip away the industry jargon and look at what your housing payment actually needs to be as a percentage of your earnings so you can sleep easy.

The Rule You Keep Seeing: The 28/36 Guideline

For decades, financial planners and mortgage lenders have relied on a classic rule of thumb to measure housing affordability: the 28/36 rule.

It’s split into two parts, and understanding both gives you an immediate reality check on your finances:

• The 28% Rule (Front-End Ratio): Your maximum housing costs—principal, interest, property taxes, home insurance, and any homeowners association (HOA) fees—should not exceed 28% of your gross (pre-tax) monthly income.
• The 36% Rule (Back-End Ratio): Your total debt payments—housing costs plus student loans, car payments, credit card minimums, and personal loans—should not exceed 36% of your gross monthly income.

Sounds simple enough, right? If you earn $5,000 a month before taxes, 28% means a housing budget of $1,400.

Here is the catch that trips people up: this rule was built for lenders, not for humans. Lenders use these percentages to decide the maximum amount they can lend you without taking on too much risk. They don't care if 28% of your gross income leaves you with zero cash for retirement savings, hobbies, or a sudden hike in your utility bills.

To see how your specific income stacks up against your debts before talking to a lender, it helps to run your full financial picture through a Debt-to-Income (DTI) Calculator — /calculators/debt-to-income-ratio-calculator to see where your current obligations actually sit.

Gross vs. Net: Why Pre-Tax Percentages Lie to You

Let’s talk about a silent stressor that ruins even the best budgets: the illusion of gross income.

When someone tells you that your mortgage should be 28% of your income, they almost always mean gross income—the big number at the top of your paystub before taxes, healthcare premiums, and retirement contributions are sliced off the top.

Imagine you land a great new job making $72,000 a year, which breaks down to $6,000 a month. Applying the 28% rule gives you a target mortgage payment of $1,680. You find a lovely home, the loan is approved, and you move in.

Then reality hits your bank account.

• Federal, state, and local taxes take $1,200.
• Your employer health insurance takes $300.
• You put 5% into your workplace retirement account to secure your future, taking another $300.

Suddenly, that $6,000 gross monthly income is actually $4,200 in net (take-home) pay.

Let’s recalculate that same $1,680 mortgage payment against your actual take-home pay. It isn’t 28% anymore. It is 40%.

Almost half of every dollar hitting your bank account is vanishing before you can buy a single carton of milk. That is the exact moment people start feeling house-poor, even though they followed the "expert" rules to the letter. If you want to see how these numbers actually play out with different loan amounts, terms, and interest rates, plugging your scenarios into a Mortgage Calculator — /calculators/mortgage-calculator can give you a crystal-clear look at the monthly damage before you fall in love with a property.

Meet Sarah: A Walkthrough of Real Numbers

To see how this works in practice, let’s follow Sarah. Sarah is a graphic designer living in a mid-sized US city. She makes a solid salary of $85,000 a year, bringing home about $5,100 a month after taxes and deductions.

Sarah currently pays $1,400 a month for a cramped apartment and is tired of her landlord raising the rent. She has saved up a $30,000 deposit and wants to buy a small starter home priced at $300,000.

Let's run the math on Sarah's dream purchase:

• Purchase Price: $300,000
• Deposit: $30,000 (10%)
• Loan Amount: $270,000
• Assumed Interest Rate: 6.5% on a 30-year fixed loan
• Principal & Interest Payment: Roughly $1,706 a month

Now, let's add the hidden costs of homeownership that apartment renters often forget:

• Property Taxes: ~$250 a month
• Homeowners Insurance: ~$100 a month
• Private Mortgage Insurance (PMI): ~$150 a month (because her deposit is under 20%)

Total Monthly Housing Payment: $2,206

Let’s check Sarah against the traditional rules:

1. Gross Income Check: Sarah earns $7,083 a month before taxes. Her $2,206 housing payment is 31% of her gross income. The lender might blink at that being slightly over the classic 28% mark, but with her clean credit score and zero other debt, they happily approve her loan.
2. Net Income Check: Sarah takes home $5,100 a month. Her $2,206 housing payment eats up 43% of her actual spendable cash.

Sarah pauses. If she takes this house, her remaining take-home pay is $2,894. Out of that, she still needs to pay for groceries, utilities, internet, car insurance, gas, medical checkups, and whatever repairs the house inevitably demands.

She realizes that a 31% gross ratio feels like a tightrope walk for her lifestyle. She decides to adjust her target purchase price down to $250,000, bringing her total monthly payment down closer to $1,850—taking up a much more comfortable 36% of her net pay instead of 43%.

The Three Hidden Costs People Always Forget

When you are trying to figure out what percentage of income your mortgage should be, the monthly principal and interest are only the opening act. Ignoring the supporting cast is how budgets derail by month three.

1. Maintenance and Repairs (The 1% Rule)

When a pipe bursts in a rental apartment, you call the landlord. When a pipe bursts in your own home, you call a plumber and hand over your weekend savings. A reliable rule of thumb is to set aside 1% of your home’s purchase price every year for maintenance. On a $300,000 home, that’s $300 a month that needs to be quietly funneled into a house emergency fund, separate from your regular savings.

2. Property Tax Creep

Property taxes do not stay still. Local governments reassess home values, and school districts pass bonds. Your property tax bill can—and usually does—creep upward every single year. If your mortgage payment is escrowed (meaning your lender collects a bit for taxes and insurance each month along with your loan payment), your monthly bill will quietly jump up right along with it.

3. Insurance Adjustments

Homeowners insurance rates across the country have climbed steeply over recent years due to severe weather events and rising rebuilding costs. Even if you don't file a claim, your annual insurance premium is likely to tick upward at renewal time, pulling your monthly payment up with it.

The Net Income Rule: What Actually Feels Comfortable?

If the 28% gross rule can lead you astray, what metric should you actually trust?

Many modern financial advisors recommend shifting your focus from gross income to net take-home pay, and aiming for the 25% to 30% net rule.

Here is why this feels so different in practice:

• Under 25% of Net Pay: This is the "sleep like a baby" zone. Your housing costs are low enough that you can absorb a sudden utility price spike, save aggressively for retirement, take a vacation without guilt, and absorb a minor financial shock without panicking.
• 25% to 35% of Net Pay: This is the standard, realistic working zone for most middle-income households, particularly in higher-cost metropolitan areas. It requires conscious budgeting—you won't be recklessly swiping your card—but it is entirely sustainable.
• Over 35% of Net Pay: This is the danger zone unless you earn a very high income where even 40% leaves you with thousands of disposable dollars a month. If you are spending 40% or 50% of a modest take-home pay on housing, one unexpected car repair or a brief period of unemployment can turn into a crisis.

Before you lock yourself into a commitment, it is always wise to zoom out and look at the big picture of your financial life using a Debt-to-Income (DTI) Calculator — /calculators/debt-to-income-ratio-calculator to ensure your future mortgage isn't crowding out every other goal you care about.

How to Make Your Mortgage Percentage Work Harder For You

What if you’ve run the numbers, and to get your mortgage down to a comfortable 28% of your gross income, you’d have to buy a home that’s entirely too small or located an hour away from your job?

You aren't entirely stuck. You have three real levers you can pull to shift the math in your favor:

• The Deposit Lever: A larger deposit doesn't just lower your monthly loan amount; it helps you bypass Private Mortgage Insurance (PMI), which can instantly shave $100 to $300 off your monthly bill.
• The Debt Lever: If you have a car payment or lingering student loans, paying them off before buying a house changes your back-end DTI ratio dramatically. Lenders look at your monthly obligations as a whole—freeing up a $400 car payment is often equivalent to qualifying for an extra $70,000 in mortgage budget without increasing your risk.
• The Term Lever: While a 30-year fixed mortgage gives you the lowest possible monthly payment, keeping an eye on long-term interest costs is crucial. Many homeowners choose a 30-year term to keep their baseline required payment safe and manageable, but use a Mortgage Overpayment Calculator — /calculators/mortgage-overpayment-calculator to see how adding just an extra $50 or $100 a month when cash flow is good can shave years off the life of the loan.

Finding Your Own Number

There is no universal magic percentage that fits every single person. Someone living in a rural area with low property taxes and zero student debt can easily carry a slightly higher housing percentage than someone living in a major city with heavy student loans and a fluctuating freelance income.

The right percentage is the one that lets you pay your mortgage on the first of the month without your stomach dropping, leaves room for the life you actually want to live outside your four walls, and still leaves a cushion for tomorrow.

Take a deep breath, run your real numbers through a Mortgage Calculator — /calculators/mortgage-calculator with your actual take-home pay in mind, and find a target that feels like breathing room, not a burden.

Disclaimer: This information is for educational purposes and doesn't constitute formal financial or mortgage advice. Every financial situation is unique, so consider speaking with an independent financial advisor before making major borrowing decisions.

---

For help running these numbers on the go, check out the free Finlaa app.

Frequently Asked Questions

Does the 28/36 rule apply if I have zero other debt?

If you have zero other debt—no car loans, no student loans, no credit card balances—you have a bit more flexibility. Because your back-end ratio (the 36% limit) matches your front-end ratio, lenders will often let you push right up against or slightly past the 28% housing limit because you have no other monthly obligations competing for your cash. However, even without debt, keeping your housing costs tied to your net income rather than gross income is still the safest way to avoid lifestyle creep.

Should I count my partner's income when calculating mortgage percentages?

Yes, but only if you are both legally co-signing the mortgage and sharing the financial responsibility long-term. If you are buying the home together, use your combined gross and net incomes to calculate your target percentage. The golden rule here is to stress-test your budget: could one of you comfortably cover the mortgage payment if the other person experienced a job loss or needed to take time off? Designing a mortgage that one income can scrape by on in an emergency is the ultimate safety net.

What is the absolute maximum percentage of net income I should spend on a mortgage?

While lenders might approve you for up to 43% or even 50% of your gross income depending on your credit score and loan program, try to keep your total housing payment under 35% of your net take-home pay as a hard ceiling. Crossing that 35% net threshold means that more than a third of everything you work for vanishes the moment rent or mortgage hits, leaving very little room for savings, emergencies, or living a full life.