28/36 Rule Calculator: How Much Mortgage Can You Afford?

Before you start browsing listings or getting pre-approved, you need to answer one critical question: how much house can I actually afford? The 28/36 rule is the simplest, most widely used guideline for answering that question. Lenders rely on it to decide whether you can handle a mortgage payment, but you should use it too — even before you talk to a bank.

In this guide, we will break down exactly what the 28/36 rule means, walk through a real-world example with an $8,000 monthly income, and show you how to apply it to your own situation so you can shop for homes with confidence.

28/36 Rule Calculator

Enter your gross monthly income and existing monthly debts to see the two limits of the 28/36 rule in dollars, plus how much room you have left for housing.

What Is the 28/36 Rule?

The 28/36 rule is a debt-to-income (DTI) guideline used by mortgage lenders across the United States. It sets two limits on how much of your gross monthly income can go toward housing and total debt payments. Think of it as a financial guardrail that keeps you from becoming house-poor.

Front-End Ratio: The 28% Rule

Your front-end ratio looks exclusively at housing costs. It says that your total monthly housing expenses — which include mortgage principal and interest, property taxes, homeowners insurance, and any HOA fees — should not exceed 28% of your gross monthly income. This group of expenses is commonly referred to as PITI (Principal, Interest, Taxes, and Insurance).

For example, if you earn $8,000 per month before taxes, your maximum housing payment under this rule would be $2,240. That is $8,000 multiplied by 0.28. This is not just your mortgage payment — it is the full cost of owning the home each month.

Back-End Ratio: The 36% Rule

Your back-end ratio takes a broader view. It includes all of your housing costs plus every other recurring debt payment you make: car loans, student loans, credit card minimums, personal loans, and any other monthly obligations. The back-end rule says that all of these combined should not exceed 36% of your gross monthly income.

Using the same $8,000 monthly income, your total debt payments — housing included — should stay at or below $2,880 per month. This means if you already have $500 in car and student loan payments, that leaves $2,380 for housing costs.

The gap between the 28% and 36% limits is where your other debts live. If you have no debt at all, you could theoretically spend up to 36% on housing. But most people have some combination of debts that eat into that ceiling.

How to Calculate Your Numbers

Calculating your affordability using the 28/36 rule takes just a few simple steps:

1. Find your gross monthly income. This is your income before taxes and deductions. If you earn $96,000 per year, divide by 12 to get $8,000 per month.
2. Calculate 28% of that number to find your maximum housing cost. For $8,000, that is $2,240.
3. Calculate 36% of that number to find your maximum total debt load. For $8,000, that is $2,880.
4. Subtract your existing monthly debts from the 36% figure to see how much room you have for housing.
5. Use the lower of the two results as your realistic maximum housing budget.

If your existing debts are minimal, the front-end (28%) number will typically be your limit. If you carry significant debt, the back-end (36%) calculation will likely be the binding constraint.

Worked Example: $8,000/Month Income

Let us walk through a detailed, realistic example to see exactly how this works in practice.

Front-End Calculation

At $1,733 per month for principal and interest, a 30-year fixed mortgage at 6.5% interest would support a loan amount of roughly $275,000 to $310,000 depending on your exact rate and whether you have PMI. Add a down payment on top of that, and you are looking at a home in the low-to-mid $300,000s.

Back-End Calculation

Now let us factor in existing debts. Say you have:

• Car loan: $350/month
• Student loans: $150/month
• Total existing debt: $500/month

In this case, the back-end calculation actually allows slightly more for housing — $2,380 versus the $2,240 from the front-end rule. So the front-end 28% limit is your binding constraint here, and your maximum housing budget remains $2,240 per month.

However, if your debts were higher — say $800/month — then the back-end ratio would limit you to just $2,080 for housing, which is less than the 28% front-end limit. That is the power of looking at both numbers together.

Taking all of this into account, a household earning $8,000 per month with moderate debts should realistically target homes in the $320,000 to $380,000 range, depending on their debt load, down payment size, and local tax rates.

Why Lenders Use This Rule

The 28/36 rule is not arbitrary — it is backed by decades of data on mortgage performance. Here is why it matters:

• Reduces default risk. Borrowers who stay within these thresholds are statistically less likely to miss payments or default on their mortgage. The rule ensures you have enough income to cover housing and still handle other obligations.
• Ensures breathing room. Life is unpredictable. The 28/36 rule leaves enough margin in your budget for unexpected expenses — a medical bill, a car repair, or a temporary reduction in income. If you are spending 50% of your income on housing, one emergency can cascade into a financial crisis.
• Standardizes underwriting. By using a consistent formula, lenders can evaluate borrowers fairly and efficiently. It creates a baseline that helps both the borrower and the lender understand what "affordable" really means.

When You Might Exceed 28/36

The 28/36 rule is a guideline, not an absolute law. There are situations where you might qualify for a mortgage even if your ratios exceed these thresholds:

• FHA loans. The Federal Housing Administration allows debt-to-income ratios up to 43% or even 50% in some cases, particularly for borrowers with strong compensating factors like a large down payment or significant cash reserves.
• Strong credit profile. If you have a credit score above 740, a substantial down payment (20% or more), and stable employment history, some conventional lenders will approve loans with a DTI up to 45%.
• VA loans. The Department of Veterans Affairs does not set a hard DTI cap, though lenders typically cap it at 41% for automated approval.

Just because you can exceed the 28/36 rule does not mean you should. Stretching your budget to the absolute maximum approved by a lender leaves very little room for error. A better approach is to use the 28/36 rule as your personal limit, even if a lender tells you that you qualify for more.

Factors the 28/36 Rule Does Not Cover

While the 28/36 rule is an excellent starting point, it does not capture the full picture of homeownership costs. Here are important expenses and considerations that fall outside this guideline:

• Emergency fund. Financial experts recommend having three to six months of expenses saved before buying a home. The 28/36 rule does not account for this safety net.
• Home maintenance. Budget 1% to 2% of your home's value per year for repairs, maintenance, and replacements. A $350,000 home could cost $3,500 to $7,000 annually in upkeep — that is $290 to $580 per month that the rule does not consider.
• Utilities. Electricity, gas, water, sewer, trash, and internet can add $200 to $400 or more to your monthly housing costs, depending on the size and location of your home.
• Job stability. The rule assumes your income is stable. If you are self-employed, work on commission, or are in an industry with high turnover, you may want to be more conservative than what the rule allows.
• Retirement savings. Contributing to a 401(k) or IRA reduces your take-home pay. The 28/36 rule uses gross income, so make sure you are still saving adequately for retirement after your mortgage payment.

Tips to Improve Your Mortgage Affordability

If your 28/36 calculations show you can afford less than you had hoped, here are actionable steps to improve your position:

1. Pay down existing debts first. Every dollar of monthly debt you eliminate frees up a dollar for housing. Paying off a $400/month car payment could increase your housing budget by that same amount.
2. Increase your income. A raise, a side hustle, or adding a co-borrower to the application can significantly boost your qualifying amount. Even a $500/month increase in gross income adds roughly $140/month to your housing budget under the 28% rule.
3. Save a larger down payment. Putting down 20% or more eliminates private mortgage insurance (PMI), reduces your monthly payment, and may qualify you for better interest rates.
4. Improve your credit score. A higher credit score unlocks lower interest rates, which means more of your payment goes toward principal rather than interest. Moving from a 680 to a 760 credit score could save you tens of thousands over the life of the loan.
5. Consider less expensive areas. If your target market is stretching your budget, look at nearby neighborhoods or suburbs where home prices are lower but the commute and amenities still work for you.

Your credit score is one of the biggest levers on your interest rate. See the minimum scores and rate impacts in our credit score and mortgages guide, or estimate your rate with our credit score mortgage calculator.

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