How Much Mortgage Can You Actually Afford Based on Your Income

What Lenders Approve vs. What You Can Afford

These are not the same number. Lenders approve loans based on risk to them, not financial health for you.

A lender's primary filter is debt-to-income ratio, or DTI. The back-end DTI includes all monthly debt obligations: mortgage principal, interest, taxes, insurance, HOA fees, student loans, car payments, and minimum credit card payments. Most conventional lenders approve borrowers up to a 43% back-end DTI. FHA loans allow up to 57% in some cases.

That means a lender will hand a $120,000-per-year earner a mortgage that consumes nearly half their gross pay before they buy groceries.

Gross income is not take-home income. A $120,000 salary produces roughly $7,400/month after federal and state taxes in most brackets. At 43% DTI on gross, the lender approves $4,300/month in total debt payments. That number bears no relationship to what that household can sustain.

The Two Ratios That Actually Matter

Front-End DTI: The Housing Cost Ratio

Front-end DTI measures housing costs alone as a percentage of gross monthly income. The target is 28% or below.

For a $120,000 gross income, 28% equals $2,800/month in total housing costs. That covers principal, interest, property taxes, homeowner's insurance, and HOA fees if applicable.

Back-End DTI: All Debt Combined

Back-end DTI adds every other monthly debt obligation. The conservative ceiling is 36%. Some financial planners use 40% as the outer limit for households with high job security and low investment priority.

The 28/36 rule is the framework that survives market stress. Lenders rarely enforce it. You must enforce it yourself.

How to Calculate Your Actual Ceiling

The formula is straightforward. Take your gross monthly income and multiply by 0.28. That product is your maximum monthly housing expense. Subtract estimated taxes and insurance, and the remainder is what you can apply to principal and interest.

Step 1. Annual gross income divided by 12 equals gross monthly income.

Step 2. Gross monthly income multiplied by 0.28 equals maximum monthly housing cost.

Step 3. Subtract estimated monthly property taxes and homeowners insurance.

Step 4. The remaining figure is your maximum monthly principal and interest payment.

Step 5. Use a mortgage amortization formula or the CalcMoney calculator to convert that payment into a loan amount at your quoted rate.

The amortization formula expressed as plain text:

Loan Amount = Monthly Payment multiplied by [(1 - (1 + r)^(-n)) / r]

Where r is the monthly interest rate (annual rate divided by 12) and n is the total number of payments (loan term in years multiplied by 12).

Worked Example 1: The $120,000 Household

Income: $120,000/year gross, or $10,000/month gross.

28% ceiling: $10,000 x 0.28 = $2,800/month total housing cost.

Estimated property taxes and insurance: $550/month (varies by state and home value).

Available for principal and interest: $2,800 - $550 = $2,250/month.

At a 7.0% interest rate on a 30-year loan, a $2,250/month principal and interest payment supports a loan amount of approximately $338,600.

With a 10% down payment, that household can target a purchase price of roughly $376,200.

A lender offering 43% DTI approval, with no other debts, would approve a monthly payment of $4,300. At 7.0%, that produces a loan amount of approximately $645,000. A purchase price near $717,000. The same borrower. Two very different financial outcomes.

The lender's number leaves that household with $3,100/month net after taxes and mortgage. Car payments, food, utilities, childcare, and retirement contributions come from that $3,100. It works until it doesn't.

Worked Example 2: The $210,000 Dual-Income Household

Income: $210,000/year combined gross, or $17,500/month gross.

28% ceiling: $17,500 x 0.28 = $4,900/month total housing cost.

Estimated property taxes and insurance: $900/month.

Available for principal and interest: $4,900 - $900 = $4,000/month.

At 7.0% on a 30-year loan, $4,000/month supports a loan of approximately $601,400.

With a 20% down payment, the target purchase price is $751,750.

This household also carries $1,200/month in existing debt (two car payments and student loans). Their back-end DTI at $4,900 housing plus $1,200 other debt equals $6,100, or 34.9% of gross. That sits inside the 36% back-end ceiling. The numbers are consistent.

A lender would likely approve this household up to a $900,000 purchase price or beyond. The conservative ceiling is $751,750. The difference is $148,250 in purchase price, and roughly $112,000 in additional interest paid over the life of the loan.

The Rate Stress Test

Your approval rate is not your permanent rate if you carry an adjustable mortgage, and even fixed-rate borrowers face refinancing risk if rates rise before they lock.

Run every affordability calculation at your quoted rate plus 1.5 percentage points.

If your quoted rate is 7.0%, confirm the numbers at 8.5%. If the payment at 8.5% breaks the 28% ceiling, the home is priced beyond your margin of safety.

For the $120,000 example: a $338,600 loan at 8.5% produces a monthly payment of approximately $2,604. Adding $550 in taxes and insurance brings total housing cost to $3,154. That exceeds the $2,800 ceiling by $354/month. This household needs either a lower purchase price, a larger down payment, or rate conditions closer to 7.0% before the purchase makes sense.

Running this stress test costs nothing. Missing it can cost tens of thousands in forced refinancing, missed savings, or sale at a loss.

What the Banks Don't Tell You About Escrow and HOA

Lenders quote principal and interest. The real payment is larger.

Property taxes average 1.07% of home value nationally, per the Tax Foundation, though they reach 2.4% in states like New Jersey and Illinois. On a $400,000 home in a high-tax state, that is $9,600/year, or $800/month in escrow.

Homeowners insurance averages $1,428/year nationally, per the Insurance Information Institute. In coastal or storm-prone markets, that figure doubles or triples.

HOA fees in managed communities average $170 to $400/month and can exceed $1,000/month in luxury developments.

A buyer who models the payment as principal and interest alone can underestimate true monthly cost by 25% to 40%. On a $450,000 home in a moderate-tax state with HOA, the gap between quoted payment and actual payment often exceeds $800/month.

Down Payment Size Changes the Equation

A larger down payment reduces the loan amount and eliminates PMI. Private mortgage insurance applies to conventional loans with less than 20% down and typically costs 0.5% to 1.5% of the loan annually.

On a $400,000 loan at 1.0% PMI, that is $4,000/year, or $333/month added to the payment. PMI cancels once the loan-to-value ratio reaches 80%, but on a 30-year amortization schedule that takes approximately 11 years without extra payments.

A borrower who can stretch a down payment from 10% to 20% on a $400,000 purchase eliminates $333/month in PMI and reduces the loan by $40,000. The combined monthly payment difference can approach $650/month. Over five years that is $39,000 in savings.

Use the Calculator to Find Your Number

The analysis above establishes the framework. The specific number depends on your gross income, existing debts, local tax rate, insurance costs, HOA situation, down payment size, current rate quote, and loan term.

The CalcMoney mortgage calculator runs all of these inputs simultaneously. It shows the 28% ceiling, the 36% back-end limit, the payment at your quoted rate, and the stress-tested payment at rate plus 1.5 points.

Enter your income, debts, down payment, and rate. The output tells you the maximum loan amount consistent with conservative affordability standards, the purchase price that supports it, and how far that sits below your lender's approval ceiling.

The gap between those two numbers is the financial risk you are accepting when you buy at approval maximum. Knowing the gap is the decision. What you do with it is yours to make.

Calculate your actual mortgage ceiling now →

You Might Also Like

• How to Calculate Your Debt-to-Income Ratio for a Mortgage (And Why Most Buyers Get It Wrong)
• 15-Year vs 30-Year Mortgage: The Exact Dollar Difference on a $400,000 Loan
• The Total Cost of a 30-Year Mortgage Is Not the Purchase Price

Results are estimates for informational purposes only. Consult a licensed financial professional before making financial decisions.