The 28/36 Rule: A Starting Point

The 28/36 rule is a commonly referenced budgeting guideline for thinking about home affordability. It is not a universal mortgage qualification standard, and actual underwriting requirements vary by lender, loan program, borrower profile, and other factors.

Gross income is what you earn before taxes and deductions. If your annual salary is $84,000, your gross monthly income is $7,000. Under the 28% rule, your total housing payment (mortgage principal and interest, property taxes, homeowners insurance, and HOA fees) should stay at or below $1,960 per month.

The 36% rule looks at all your debts together. If you have a $400 car payment and a $200 student loan payment, your total debt including housing should stay at or below $2,520 per month ($7,000 × 0.36). Since your car and student loans already take $600, your maximum housing payment under this rule would be $1,920.

These guidelines are a starting point, not a hard limit. Some loan programs allow total DTI up to 43% or even 50% with compensating factors such as a high credit score or large cash reserves. But stretching to the maximum can leave you house-poor.

How Lenders Calculate Debt-to-Income Ratio

Debt-to-income ratio (DTI) is one of the key measures lenders use when evaluating how much debt a borrower may be able to manage. It compares your monthly debt obligations to your gross monthly income.

There are two versions of the ratio. The front-end ratio (also called the housing ratio) includes only your housing costs. The back-end ratio (the total debt ratio) includes housing plus all other debts: car loans, student loans, credit card minimums, child support, and any other recurring obligations.

To calculate your own DTI, add up all monthly debt payments that appear on your credit report, plus the estimated monthly housing payment for the home you are considering. Divide that total by your gross monthly income and multiply by 100 to get a percentage.

For example, with a gross monthly income of $6,500, a projected housing payment of $1,800, a car payment of $350, and a student loan payment of $250, your total monthly debt is $2,400. Your DTI is $2,400 ÷ $6,500 × 100 = 36.9%. Most conventional lenders would accept this, though you are close to the typical 43% ceiling.

Factors That Affect How Much You Can Borrow

Several variables work together to determine your maximum loan amount. Understanding each one helps you see where you have room to improve.

The Hidden Costs of Homeownership

The mortgage payment is just the beginning. True ownership costs include several expenses that renters do not face, and failing to budget for them is the most common reason new owners feel house-poor.

Maintenance and repairs typically cost 1% to 2% of the home's value per year. On a $350,000 home, that is $3,500 to $7,000 annually — roughly $290 to $580 per month. Some months you will spend nothing; other months you will need a new water heater or roof repair. Set aside money monthly so you are ready.

Utilities — electricity, gas, water, trash, internet — are often higher in a house than in an apartment. Budget for larger square footage, outdoor irrigation, and less efficient systems in older homes.

HOA dues, if applicable, can add $100 to $500 or more per month. These fees can increase annually and may include special assessments for major repairs.

Property taxes can rise over time as the home's assessed value increases. Budget for modest annual increases, especially if your area has a history of rising assessments.

A Worked Affordability Example

Let us walk through a realistic example. Suppose your gross annual income is $90,000 ($7,500 per month). You have a $350 car payment and a $200 student loan payment. You have saved $40,000 for a down payment and closing costs.

Under the 28% rule, your maximum housing payment is $2,100. Under the 36% rule, your maximum total debt is $2,700, so after your $550 in existing debts, your maximum housing payment is $2,150. The 28% rule is the binding constraint at $2,100.

Now subtract estimated property taxes and insurance. In an area with a 1.1% tax rate on a $350,000 home, taxes are about $3,850 per year or $320 per month. Homeowners insurance might be $1,400 per year or $117 per month. That leaves about $1,663 for principal and interest.

At a 6.5% interest rate on a 30-year loan, a $1,663 monthly principal-and-interest payment supports a loan of about $262,000. Add your down payment — say $25,000 after closing costs — and your maximum affordable home price is roughly $287,000. This is lower than many people expect, which is why running the numbers before shopping is so important.

You can model your own scenario with our Affordability Calculator and then verify the monthly payment with our Mortgage Calculator.

Avoiding the House-Poor Trap

Being house-poor means your mortgage payment is technically affordable under lender rules, but it consumes so much of your income that you have nothing left for saving, investing, travel, or emergencies. Lenders approve you based on gross income, but you live on net income — what is left after taxes and deductions.

A good safeguard is to base your personal affordability calculation on take-home pay, not gross income. Some households use a conservative budgeting guideline of keeping housing costs near 25% of take-home pay, but there is no universal percentage that works for everyone. Your appropriate housing budget depends on your income, debts, savings goals, family needs, location, and other expenses. This leaves room for retirement contributions, an emergency fund, and the lifestyle you want.

Also consider future life changes. If you plan to have children, switch to a single income, or relocate in five years, factor that into your decision. A home that is affordable today may become a burden if your circumstances change.