The mortgage you can afford depends on your income, debts, and down payment—not on what a lender will give you

A lender will often approve you for more than you should borrow. Banks use two main ratios: your housing costs (mortgage, taxes, insurance) should not exceed 28% of your gross monthly income, and your total debt payments should not exceed 36%. These are ceilings, not targets. A mortgage that fits the 28% rule can still leave you house-poor if you have student loans, car payments, or irregular income. The real question is not what the bank will lend, but what monthly payment leaves you able to save, handle emergencies, and live the life you want.

Your affordability is the intersection of three things: what a lender will approve, what your budget actually allows, and what leaves you financially secure. This article walks you through each one so you can find the number that is right for your situation, not just the maximum a bank will hand you.

Key Takeaways

  • Lenders typically approve mortgages up to 28% of your gross income for housing costs alone, but this does not account for your other debts or your actual living expenses.
  • Your down payment size directly affects your monthly payment: a 20% down payment avoids mortgage insurance, while smaller down payments add hundreds to your monthly cost.
  • Property taxes, homeowners insurance, and HOA fees are not optional and vary widely by location—a house that costs $300,000 in one state may carry $500 more per month in taxes in another.
  • A useful rule of thumb is that your total housing payment should not exceed 25% to 28% of your gross income, and your total debt payments should stay below 36%.
  • Use a mortgage calculator to test different loan amounts, interest rates, and down payments, then subtract that payment from your actual monthly budget to see what remains.

How lenders calculate what they will lend you

Lenders use your income and existing debts to set a maximum loan amount. They pull your credit report, verify your employment and income (usually the past two years of tax returns), and list all your monthly debt payments: car loans, student loans, credit cards, child support, and anything else that appears on your credit file.

The debt-to-income ratio is the key number. Your housing payment (principal, interest, taxes, insurance, and mortgage insurance if applicable) divided by your gross monthly income should not exceed 28%. Your total monthly debt payments divided by gross income should not exceed 36%. If you earn $5,000 per month gross, a lender will typically allow a housing payment of up to $1,400 (28% of $5,000) and total debt payments of up to $1,800 (36% of $5,000). If you already owe $300 per month on a car loan and $200 on student loans, you have only $1,300 left for a mortgage payment.

These ratios are industry standards, but individual lenders vary. Some will go as high as 43% debt-to-income for borrowers with excellent credit and substantial savings. Others stay stricter. The ratio also does not account for the cost of living where you are—$1,400 per month in housing costs stretches further in rural Kentucky than in suburban Boston.

What actually goes into your monthly housing payment

Your mortgage payment is not just principal and interest. It includes four components, often called PITI: principal, interest, taxes, and insurance. Many lenders also require PMI (private mortgage insurance) if your down payment is less than 20%.

Principal and interest are straightforward: they depend on the loan amount, interest rate, and loan term. A $300,000 loan at 7% interest over 30 years costs about $1,996 per month in principal and interest alone. Property taxes vary dramatically by location—from less than 0.5% of home value per year in Hawaii to over 2% in New Jersey. On a $300,000 home, that is a difference of $125 to $500 per month. Homeowners insurance typically runs $100 to $200 per month depending on the home's age, location, and your coverage level. If you put down less than 20%, you will pay PMI, which can add $150 to $400 per month depending on the loan amount and your credit score.

If your home is in a planned community or condo building, add HOA fees, which range from $50 to $500+ per month. These are not optional and do not build equity. When you calculate what you can afford, include every one of these costs, not just the principal and interest. A home that looks affordable at $1,500 per month in principal and interest becomes unaffordable when you add $400 in taxes, $150 in insurance, $250 in PMI, and $200 in HOA fees.

How your down payment changes what you can afford

The size of your down payment directly affects your monthly payment and your total borrowing power. A larger down payment means a smaller loan, lower monthly payments, and no mortgage insurance.

Suppose you want to buy a $300,000 home and can afford a $1,500 monthly housing payment. With a 20% down payment ($60,000), you borrow $240,000. At 7% interest over 30 years, that is roughly $1,596 per month in principal and interest—before taxes, insurance, and HOA. With a 10% down payment ($30,000), you borrow $270,000, which costs about $1,797 per month in principal and interest, plus PMI of about $200 per month. Your payment just jumped $400 per month, and you have not yet added property taxes or insurance.

If you have saved less than 20%, you have two choices: save longer and buy a less expensive home now, or accept PMI and plan to refinance once you have built 20% equity. PMI is not permanent—once your loan balance drops to 80% of the home's value, you can request removal. But it does cost money in the meantime, so factor it into your affordability calculation. The trade-off is real: buying sooner with PMI versus waiting longer to avoid it.

The difference between what you can afford and what you should borrow

A lender's approval is not a recommendation. Banks are in the business of lending money, not protecting your financial security. A mortgage that fits the 28% debt-to-income ratio can still be too large if you have irregular income, high job insecurity, or other financial obligations the ratio does not capture.

Consider your actual monthly expenses: groceries, utilities, gas, insurance, childcare, student loan payments, car maintenance, medical costs, and everything else you actually spend money on. Subtract those from your gross income. What remains is what you can realistically put toward a mortgage payment and still have money left for savings and emergencies. If your gross income is $5,000 per month and your non-housing expenses total $2,500, you have $2,500 left. The lender might approve you for a $1,400 housing payment (28% of $5,000), but that leaves you only $1,100 per month for savings, emergencies, and any expense you underestimated. Many financial advisors recommend keeping your housing payment to 25% of gross income or lower, which would be $1,250 in this example.

A useful test: subtract your proposed mortgage payment (including taxes, insurance, and PMI) from your take-home pay. Can you still save 10% to 15% of your income? Can you cover a $1,000 emergency without going into debt? If the answer is no, the house is too expensive, regardless of what the lender approves. Your actual affordability is the number that lets you sleep at night, not the maximum the bank will hand you.

How interest rates affect your affordability

Interest rates move constantly and directly change your monthly payment. A 1% difference in interest rate can add or subtract $200 per month on a $300,000 loan. When rates are high, you can afford to borrow less. When rates are low, the same income supports a larger loan.

If you are shopping for a home, get pre-approved for a mortgage so you know your actual interest rate, not a hypothetical one. Pre-approval involves a credit check and income verification and is valid for 60 to 90 days. It tells you the real monthly payment you would face at today's rates. Do not rely on online calculators that use average rates—use the rate your lender quotes you. Also understand that your rate may change between pre-approval and closing, especially if you lock in a rate and then wait months to close. Ask your lender about rate locks and how long they last.

Using a mortgage calculator to test your real situation

Start with a mortgage calculator that includes property taxes, insurance, and PMI, not just principal and interest. Enter your down payment amount, the loan term (15 or 30 years), and your expected interest rate. Most lenders' websites offer calculators, and sites like Bankrate and NerdWallet have detailed ones that let you input your location so taxes are more accurate.

Run several scenarios: what if rates go up 1%? What if you put down 15% instead of 20%? What if you buy a home $50,000 cheaper? For each scenario, write down the total monthly payment. Then look at your actual budget. How much can you comfortably pay each month and still meet your other goals? The answer to that question is your real affordability ceiling, and it may be lower than what a lender will approve. The calculator is a tool to test reality, not to find the biggest number you can borrow.

Frequently Asked Questions

What if my income is irregular or I am self-employed?

Lenders typically average your income over two years and may use a lower figure if your income is declining. Self-employed borrowers often need two years of tax returns and may face stricter debt-to-income limits. If your income varies, use a conservative estimate—your lowest recent year—when calculating what you can afford, not your best year.

Should I aim for a 15-year or 30-year mortgage?

A 15-year mortgage has a higher monthly payment but costs far less in interest over the life of the loan. A 30-year mortgage has a lower monthly payment, leaving more room in your budget for savings and emergencies. The right choice depends on your income stability and other financial goals. If you can comfortably afford the 15-year payment and still save, it is a faster path to owning your home outright. If the 15-year payment would strain your budget, the 30-year option is safer.

Can I afford a home if I have student loan debt?

Yes, but your student loan payments count toward your debt-to-income ratio. If you owe $300 per month in student loans and earn $5,000 gross per month, your remaining debt capacity is $1,500 (36% of $5,000 minus $300). Your housing payment must fit within that $1,500. If you are on an income-driven repayment plan, lenders may use a different calculation—ask your lender how they treat your specific loan type.

What happens if I get a raise after I buy?

A raise does not change your mortgage payment, but it does give you more breathing room in your budget. This is one reason to be conservative when you first buy: a mortgage that feels tight at your current income becomes more comfortable as you earn more. Do not count on future raises when deciding what to borrow now.

Is it better to put down 20% or the minimum required?

Twenty percent avoids PMI and gives you immediate equity, but it requires more savings upfront. If you can afford to wait and save 20%, you will pay less over the life of the loan. If you need to buy sooner and can afford the PMI, a smaller down payment is reasonable—just make sure your total monthly payment still fits your budget and leaves room for savings.