Budget planning

Estimate a comfortable home budget

This planner compares your income, existing debts, and target housing ratio to estimate a home price that may fit your budget.

How Much Home Can You Afford?

Determining your target home purchase budget relies on lender underwriting guidelines rather than maximum pre-approval limits alone. Lenders evaluate your gross income, existing debt obligations, liquid down payment reserves, and target credit score to assess borrowing risk.

The 28/36 Rule

The standard benchmark used in residential mortgage underwriting is the 28/36 Rule:

• Front-End Ratio (28% Rule): Total monthly housing costs (Principal, Interest, Taxes, Insurance, HOA fees, and PMI) should not exceed 28% of your gross monthly income.
• Back-End Ratio (36% Rule): Total monthly debt obligations (housing costs plus student loans, credit cards, auto loans, and personal loans) should not exceed 36% of your gross monthly income.

Affordability Formulas

$$\text{Max Front-End Housing Cap} = \text{Gross Monthly Income} \times 0.28$$

$$\text{Max Back-End Total Cap} = \text{Gross Monthly Income} \times 0.36$$

$$\text{Maximum Allowed Housing Payment} = \min\left(\text{Max Front-End Cap}, \text{Max Back-End Cap} - \text{Existing Monthly Debt}\right)$$

Step-by-Step Affordability Example

Consider a household evaluating their home purchase budget:

• Gross Household Annual Income: $100,000 ($8,333.33/month)
• Existing Monthly Debt Obligations: $500 (Auto loan: $300 + Student loan: $200)

Front-End Calculation:

$$\$8,333.33 \times 0.28 = \$2,333.33/\text{month}$$

Back-End Calculation:

$$(\$8,333.33 \times 0.36) - \$500.00 = \$3,000.00 - \$500.00 = \$2,500.00/\text{month}$$

Maximum Allowed Housing Payment:

Taking the lower of the two underwriting limits yields $2,333.33/month for total housing costs.

Working backward from a $2,333.33 maximum payment under the following terms:

• Interest Rate: 6.50% (30-year fixed)
• Down Payment: 10% ($31,000)
• Property Taxes: 1.20% per year ($310.00/month)
• Homeowners Insurance: $100.00/month
• Private Mortgage Insurance (PMI): 0.69% per year ($159.86/month)

This buyer can afford a maximum purchase price of approximately $310,000.

Frequently Asked Questions

What is Debt-to-Income (DTI) ratio, and why does it matter?

Your Debt-to-Income (DTI) ratio is the percentage of your gross monthly income spent on recurring debt payments. A lower DTI indicates greater financial flexibility, qualifying you for lower interest rates and higher maximum loan amounts.

Can I qualify for a home with a DTI ratio higher than 36%?

Yes. Conventional loans backed by Fannie Mae or Freddie Mac often accept total DTI ratios up to 45% to 50% with compensating factors like high credit scores or strong cash reserves. FHA loans also offer higher DTI allowances. However, spending over 36% increases your risk of becoming "house poor."

How does interest rate volatility affect buying power?

Interest rates directly control your monthly principal and interest costs. As a general rule of thumb, every 1% increase in interest rates reduces your total home purchasing power by roughly 10% for the same target monthly payment.

What cash reserves should I keep after making a down payment?

Lenders prefer borrowers to hold 3 to 6 months of housing expenses in liquid savings after closing. These emergency reserves ensure you can cover mortgage obligations during unexpected job changes or home repairs.