What determines how much a lender will lend you

A lender will offer you a mortgage based on your income, debts, credit score, and the down payment you have saved. Most lenders use a formula called the debt-to-income ratio (DTI), which compares your monthly debt payments to your gross monthly income. If your DTI is too high, you will not be offered as much, even if you have a large down payment.

The standard ceiling for most conventional mortgages is a DTI of 43 percent. That means your total monthly debt payments — including the new mortgage payment, property taxes, insurance, homeowners association fees, car loans, student loans, credit cards, and any other recurring obligations — cannot exceed 43 percent of your gross monthly income. Some lenders will go to 50 percent if you have a strong credit score and substantial savings, but 43 percent is the norm.

Your credit score also affects the interest rate you are offered and sometimes the maximum loan amount. A score below 620 makes conventional mortgages difficult to find; FHA loans (backed by the Federal Housing Administration) may still be available but with higher rates and stricter terms. A score of 740 or above typically unlocks the best rates and the most flexibility on loan size.

Key Takeaways

  • Lenders calculate how much to lend you using your debt-to-income ratio, which compares all your monthly debt payments to your gross monthly income, with a typical ceiling of 43 percent.
  • Your down payment size affects the loan amount directly — a larger down payment means you need to borrow less, but it does not change the maximum you can borrow based on income.
  • Credit scores below 620 make conventional mortgages scarce, while scores of 740 or above unlock better rates and higher borrowing limits.
  • You can calculate your own maximum by multiplying your gross monthly income by 0.43, subtracting your other monthly debts, and dividing the result by your expected monthly mortgage payment rate.
  • The amount a lender offers you is not the same as the amount you should borrow — your own budget and emergency savings matter more than the lender's ceiling.

How to calculate your own maximum using debt-to-income

Start with your gross monthly income — the total before taxes and deductions. Multiply that number by 0.43. That is your maximum total monthly debt payment under the standard DTI rule.

Next, add up all your other monthly debt payments: car loans, student loans, credit card minimums, personal loans, child support, alimony, and any other recurring obligation. Subtract that total from your maximum debt payment. The result is the maximum you can spend on your new mortgage payment each month.

To convert that into a loan amount, you need to know the mortgage payment factor for your expected interest rate and loan term. For a 30-year mortgage at 7 percent interest, the payment factor is roughly 0.0066 per $1,000 borrowed — meaning a $300,000 loan costs about $1,980 per month. At 6 percent, the factor is roughly 0.0060, or about $1,800 per month for $300,000. Online mortgage calculators can give you the exact factor for your rate.

Divide your maximum monthly mortgage payment by the payment factor to find the loan amount. If your maximum payment is $2,000 and the factor is 0.0066, you can borrow roughly $303,000. Remember that this calculation does not include property taxes, homeowners insurance, or HOA fees — those are part of your monthly housing cost and will reduce the actual loan amount a lender offers.

How down payment size changes what you can borrow

Your down payment does not change the maximum loan amount a lender will offer based on your income and DTI. It changes the total home price you can afford. If a lender will lend you $300,000 and you have $60,000 saved for a down payment, you can buy a $360,000 home. If you have $100,000 saved, you can buy a $400,000 home with the same $300,000 loan.

A larger down payment does have other benefits: it lowers your monthly payment, reduces the interest you pay over the life of the loan, and may allow you to avoid private mortgage insurance (PMI). PMI is required when your down payment is less than 20 percent of the home price, and it adds roughly 0.5 to 1 percent of the loan amount to your annual costs. A 10 percent down payment on a $300,000 loan means paying PMI until you have paid down the loan to 80 percent of the original home value.

Some loan programs have minimum down payment requirements. Conventional mortgages typically require at least 3 percent down. FHA loans require 3.5 percent down. VA loans (for military members and veterans) often require zero down payment. USDA loans (for rural homebuyers) also often require zero down. Your down payment size may determine which programs you are even offered.

Why the lender's maximum is not your budget

A lender will tell you the maximum they will lend based on your income and debts. That number is not a recommendation for how much you should borrow. It is a ceiling, not a target.

The lender's calculation includes property taxes, homeowners insurance, and mortgage interest, but it does not account for maintenance, repairs, utilities, property taxes that may rise, or the fact that you have other financial goals. A home that costs the maximum you can borrow leaves little room for emergencies, retirement savings, or anything else.

A common rule of thumb is to spend no more than 28 percent of your gross monthly income on housing costs (mortgage, taxes, insurance, HOA). This is stricter than the lender's 43 percent DTI and leaves more of your income for other debts and savings. If you earn $5,000 per month, the 28 percent rule suggests a housing payment of $1,400, while a lender might offer you up to $2,150 based on your other debts.

What happens if you have high existing debt

If you carry substantial student loans, car payments, or credit card balances, your DTI will be high even if your income is strong. A $200,000 salary sounds like plenty until you subtract $3,000 per month in student loan payments, $600 in a car loan, and $400 in credit card minimums. That is $4,000 in existing debt, leaving only $6,700 of your $16,667 gross monthly income available for a mortgage payment under the 43 percent rule.

Paying down high-interest debt before you apply for a mortgage can increase the loan amount you are offered. Paying off a $400 credit card minimum frees up $400 per month for a mortgage payment, which translates to roughly $60,000 more in borrowing power (depending on your interest rate). Paying off a $600 car loan frees up $600 per month, or roughly $90,000 more in borrowing power.

If you cannot pay down debt before buying, you may need to wait, buy a less expensive home, or look for a co-borrower with lower existing debt. Some lenders will exclude student loan payments if you are on an income-driven repayment plan and have been making payments for at least two years, but this varies by lender and loan type.

How credit score affects your borrowing power

Your credit score determines the interest rate you are offered, which directly affects your monthly payment and therefore your borrowing power. A score of 760 might get you a 6.5 percent rate, while a score of 680 might get you 7.5 percent. That one percentage point difference costs roughly $100 per month on a $300,000 loan, which reduces your borrowing power by about $15,000.

Beyond the interest rate, a low credit score can limit which loan programs are available to you. Conventional mortgages typically require a score of 620 or higher. FHA loans allow scores as low as 580, but with higher insurance costs and stricter terms. If your score is below 580, you may be limited to FHA loans or may not be offered a mortgage at all.

Improving your credit score before you apply takes time but pays off. Paying down credit card balances (especially to below 30 percent of your credit limit), making all payments on time for several months, and not opening new accounts can raise your score by 50 to 100 points in three to six months. Each 50-point increase can lower your interest rate by 0.25 to 0.5 percent, which translates to thousands of dollars in savings over the life of the loan.

Frequently Asked Questions

Can I get a mortgage if I am self-employed?

Yes, but lenders require more documentation. You will typically need two years of tax returns, profit-and-loss statements, and sometimes a CPA letter confirming your income. Some lenders average your income over two years, which can lower your borrowing power if your income has been rising. Shop with lenders who specialize in self-employed borrowers — they understand variable income better than banks that only see W-2 employees.

What if I have no credit history or a very thin credit file?

Lenders can use alternative credit data — utility payments, rent history, insurance payments, and phone bills — to build a credit profile if you have no traditional credit score. FHA loans are more flexible with thin files than conventional mortgages. You may also need a larger down payment (10 to 15 percent instead of 3 percent) to offset the lender's uncertainty about your payment history.

Does getting pre-approved lock in an interest rate?

Pre-approval tells you the maximum a lender will offer and usually includes a rate quote, but the rate is typically locked only for 30 to 60 days. If you do not find a home and make an offer within that window, you will need to re-apply and may receive a different rate. Rate locks are usually free for 30 days and cost a fee (0.25 to 0.5 percent of the loan) if you want to lock for longer.

Can I borrow more if I have a co-borrower?

Yes. A co-borrower's income is added to yours, and their debts are added to the calculation. If you earn $60,000 and your spouse earns $80,000, your combined gross income is $140,000, which increases your borrowing power. However, if your spouse also carries debt, that reduces the benefit. Both borrowers' credit scores are checked, and the lower score may determine your interest rate.

What if the lender's offer is less than I expected?

Ask the lender to break down the calculation — show you your DTI, your credit score, and which debts are being counted. If debts are listed incorrectly or if you have paid something off recently, ask them to update the information and recalculate. If your score is lower than you thought, check your credit report at annualcreditreport.com (the only free source mandated by federal law) and dispute any errors. If your income is seasonal or variable, ask whether the lender can use a different calculation method.