The two numbers that matter: income and debt

Most lenders use two ratios to decide how much house you can afford. The first is your front-end ratio: your monthly housing payment (mortgage, property tax, insurance, and homeowners association fees) divided by your gross monthly income. Most lenders cap this at 28 percent. The second is your back-end ratio: all your monthly debt payments (housing plus car loans, credit cards, student loans, and other obligations) divided by gross monthly income. Most lenders cap this at 36 to 43 percent, depending on the loan type.

These ratios are the floor and ceiling of what a lender will offer you. You may may have access to for a loan that reaches the ceiling, but that does not mean you should take it. The difference between what you can borrow and what you can actually afford to pay without financial strain is often substantial.

To find your own numbers, gather your most recent pay stubs to confirm your gross monthly income, and list every debt payment you make each month: car loans, student loans, credit cards (use the minimum payment, not the balance), personal loans, and any other recurring obligations. You will need these figures for every calculation that follows.

Key Takeaways

  • Lenders typically allow housing costs up to 28 percent of your gross monthly income and total debt up to 36 to 43 percent, but these are ceilings, not targets.
  • Your down payment size directly affects the loan amount you need and the monthly payment, so a larger down payment lowers the price range you can afford.
  • Property taxes, homeowners insurance, and mortgage insurance (if your down payment is under 20 percent) are part of your monthly housing cost, not just the loan payment itself.
  • A mortgage calculator that includes taxes, insurance, and HOA fees gives you a realistic monthly cost; using only the loan payment understates what you will actually owe.
  • Your credit score affects the interest rate you receive, which can change your affordable price range by tens of thousands of dollars.

Working backward from your income: the 28 percent rule

Start with your gross monthly income. If you earn $60,000 per year, your gross monthly income is $5,000. Twenty-eight percent of that is $1,400. This is the maximum monthly housing payment most lenders will allow.

But $1,400 is not the same as your mortgage payment. It includes your mortgage principal and interest, property tax, homeowners insurance, and mortgage insurance (if applicable). In many states, property tax alone eats 15 to 25 percent of that $1,400. In others, it takes much less. This is why the same income supports different house prices in different states.

To estimate what house price fits your income, you need to know your local property tax rate and typical homeowners insurance cost. Your county assessor's office publishes the property tax rate (often listed as a percentage of home value or as a dollar amount per $1,000 of assessed value). Insurance costs vary by location, age of the home, and coverage level, but you can call a local insurance agent for a rough quote on a home in your target price range.

How down payment size changes what you can afford

A larger down payment lowers the loan amount you need, which lowers your monthly payment, which means you can afford a higher purchase price within the same 28 percent ceiling. Conversely, a smaller down payment raises the loan amount and the monthly payment, shrinking the price range you can afford.

If you put down 20 percent, you avoid mortgage insurance (PMI). If you put down less than 20 percent, the lender adds mortgage insurance to your monthly payment. This insurance protects the lender if you default; it does not protect you. The cost varies by loan type and down payment percentage, but it typically adds $100 to $300 per month on a $300,000 loan.

Example: On a $300,000 home with a 3 percent down payment ($9,000), you borrow $291,000. With a 7 percent interest rate over 30 years, the loan payment alone is about $1,935 per month. Add property tax, insurance, and PMI, and your total housing payment could reach $2,400 to $2,600 per month. With a 20 percent down payment ($60,000), you borrow $240,000, your loan payment drops to $1,596, and your total housing payment might be $1,900 to $2,000 per month — a difference of $400 to $600 per month, or $4,800 to $7,200 per year.

The back-end ratio: what your other debts cost you

Even if your housing payment fits the 28 percent rule, your total debt may exceed the 36 to 43 percent back-end limit. If you carry $400 per month in car payments, $200 in student loans, and $150 in credit card minimums, that is $750 in non-housing debt. Add a $1,400 housing payment, and your total debt is $2,150 per month. On a $5,000 gross monthly income, that is 43 percent — at the ceiling for most conventional loans.

If you are near the back-end limit, paying down debt before you buy will increase the house price you can afford. Every $100 per month you eliminate from non-housing debt frees up $100 per month for a housing payment. On a 7 percent, 30-year mortgage, an extra $100 per month in payment capacity lets you borrow roughly $17,000 more.

Some lenders offer slightly higher back-end ratios (up to 50 percent) if you have strong credit, significant savings, or a low debt-to-income ratio overall. But these exceptions require you to ask, and they are not may provide.

Using a mortgage calculator with all the real costs

A basic mortgage calculator shows only the loan payment (principal and interest). A better one includes property tax, homeowners insurance, and PMI. Use the second kind, because the first understates your actual monthly cost by hundreds of dollars.

To use a realistic calculator, you need: your down payment amount (in dollars or as a percentage), the interest rate you expect to receive (which depends on your credit score and current market rates), the loan term (usually 15 or 30 years), your local property tax rate, an estimate of homeowners insurance, and your HOA fee if applicable.

Plug in a house price, and the calculator shows your total monthly payment. Adjust the price up or down until the payment reaches your 28 percent ceiling. That price is your affordability limit based on income alone. Then check it against the 36 to 43 percent back-end limit by adding your non-housing debt payments. If the total exceeds your back-end ceiling, lower the house price until it fits.

How interest rate and credit score shift your price range

Interest rates change daily and vary based on your credit score. A borrower with a 740 credit score might receive a 6.5 percent rate, while a borrower with a 620 score might receive 7.5 percent on the same loan. That one percentage point difference costs roughly $100 more per month on a $300,000 loan.

Over the life of a 30-year mortgage, a higher interest rate means you pay tens of thousands of dollars more in total interest. It also means your monthly payment is higher, which shrinks the house price you can afford within your 28 percent ceiling.

If your credit score is below 700, paying down debt and correcting errors on your credit report before you apply for a mortgage can raise your score and lower your interest rate. Even a 20 to 30 point improvement can save you $50 to $100 per month. Check your credit report at annualcreditreport.com (the only free, federally authorized source) and dispute any errors before you shop for a mortgage.

The gap between what you can borrow and what you should borrow

A lender may approve you for a $400,000 mortgage, but that does not mean a $400,000 house is the right choice for your finances. Lenders use ratios that work for the average borrower, not for your specific situation. If you have irregular income, a job that is not secure, or large expenses coming (a child starting college, aging parents needing care), borrowing at the ceiling leaves no room for unexpected costs.

A common rule of thumb is to aim for a house payment that is no more than 25 percent of your gross income, not 28 percent. This gives you a 3 percent buffer. Similarly, keeping your total debt below 36 percent instead of 43 percent leaves room for emergencies. These tighter targets mean you can afford less house, but you sleep better when an unexpected expense arrives.

Before you settle on a price, also consider the costs of homeownership beyond the monthly payment: maintenance and repairs (typically 1 to 2 percent of the home's value per year), utilities, and property tax increases over time. A house you can barely afford on paper often becomes a financial burden in practice.

Frequently Asked Questions

Does my student loan debt count toward the back-end ratio?

Yes. Lenders count the actual monthly payment you make on student loans, not the full balance. If you are on an income-driven repayment plan, they use your current payment amount. If you are not yet in repayment (in school or during a grace period), some lenders estimate a payment based on the loan balance, which can be higher than what you actually owe.

What if I have irregular income or am self-employed?

Lenders typically average your income over the past two years and may require two years of tax returns. If your income is rising, they use the lower of the two years. If it is falling, they may decline the loan. Some lenders specialize in self-employed borrowers and use different criteria, such as bank statements or profit-and-loss statements, so shop around if traditional lenders reject you.

Can I afford a house if I have no down payment saved?

Some loan programs allow down payments as low as 3 percent (conventional loans) or 0 percent (VA loans for may be able to access veterans, USDA loans in rural areas). However, a smaller down payment means a larger loan, a higher monthly payment, and mortgage insurance, all of which shrink the house price you can afford within your income limits. Saving a larger down payment before you buy increases your price range and lowers your long-term costs.

How much should I budget for property tax and insurance?

Property tax varies widely by state and county — from under 0.5 percent of home value per year in some areas to over 2 percent in others. Homeowners insurance typically costs $800 to $1,500 per year for a $300,000 home, but varies by location, age of the home, and coverage level. Call a local insurance agent and check your county assessor's website for your area's tax rate to get accurate numbers for your calculation.

What if I want to buy a house but my debt-to-income ratio is too high?

Pay down non-housing debt before you apply. Every dollar you eliminate from monthly debt payments increases the house price you can afford. Paying off a car loan ($400 per month) or credit cards ($200 per month) can free up $600 per month for a housing payment, which translates to roughly $100,000 more in borrowing power on a 30-year mortgage at 7 percent interest.