What determines your mortgage size

A lender will offer you a mortgage based on your income, debts, credit score, and the down payment you have saved. The size of the loan depends mostly on how much monthly income you can prove and how much of that income you can afford to put toward a mortgage payment. Lenders use formulas called debt-to-income ratios to decide this — they want to see that your housing payment won't exceed a certain percentage of your gross monthly income, typically between 28 and 43 percent depending on the lender and loan type.

Your credit score affects not just whether you get approved, but also the interest rate you'll pay. A higher score usually means a lower rate, which makes your monthly payment smaller and can increase the size of the loan you can afford. Your down payment also matters: a larger down payment means you borrow less, but it also shows the lender you have savings and skin in the game, which can improve your terms.

Key Takeaways

  • Lenders calculate how much to offer based on your gross monthly income and existing debts, using a debt-to-income ratio that typically caps your housing payment at 28 to 43 percent of what you earn before taxes.
  • Your credit score affects both whether you get approved and the interest rate you receive, which directly changes how large a loan you can afford.
  • The down payment you have saved determines how much you need to borrow and signals to the lender how financially stable you are.
  • Pre-approval from a lender gives you a concrete number before you start house hunting, and that number is based on documents they actually verify, not estimates.

How lenders calculate the mortgage amount

Lenders use your gross monthly income — the money you earn before taxes and deductions — as the starting point. If you earn $60,000 a year, that's $5,000 gross per month. A lender using a 28 percent housing ratio would allow a mortgage payment of up to $1,400 per month. That payment covers principal, interest, property taxes, homeowners insurance, and mortgage insurance if your down payment is less than 20 percent.

The second calculation is your debt-to-income ratio, or DTI. This looks at all your monthly debt payments — car loans, student loans, credit cards, personal loans — and adds your proposed mortgage payment to them. The total cannot exceed 43 percent of your gross income for most conventional loans, though some lenders go as high as 50 percent. If you have $500 in existing debts and a $1,400 mortgage payment, that's $1,900 total, which must stay under 43 percent of your gross income.

The actual dollar amount you can borrow depends on the interest rate you're offered. A lower rate means a smaller monthly payment for the same loan size, so you can borrow more. Interest rates change daily and depend on your credit score, down payment size, loan type, and current market conditions. This is why pre-approval matters: a lender will lock in a rate estimate and tell you the exact loan amount you may have access to for.

What pre-approval actually tells you

Pre-approval is a lender's written statement that you meet their basic requirements for a specific loan amount. To get pre-approved, you'll provide pay stubs, tax returns, bank statements, and a credit authorization. The lender verifies your income, checks your credit report, and reviews your debts. They then offer you a loan amount — say, $350,000 — at an estimated interest rate, usually good for 60 to 90 days.

Pre-approval is not a promise to lend. The lender can still back out if your financial situation changes, if you take on new debt, or if the property appraisal comes in lower than the purchase price. But it does give you a real number based on documents the lender has actually seen, not a calculator estimate. This number is what you should use when you start looking at houses.

Many people confuse pre-approval with pre-qualification, which is just a rough estimate based on information you provide over the phone or online. Pre-qualification is free and takes minutes, but it's not binding and doesn't verify anything. If you're serious about buying, get pre-approved.

How your credit score affects the loan size

Your credit score determines the interest rate you're offered, and the interest rate directly affects how much you can borrow. If you have a score of 760 or higher, you might get a rate of 6.5 percent on a 30-year mortgage. If your score is 620 to 639, you might get 8.5 percent. That difference of 2 percentage points cuts your monthly payment by roughly $200 on a $350,000 loan, which means you could afford to borrow $50,000 more at the same monthly payment.

Lenders also use credit score to decide whether to approve you at all. Most conventional loans require a score of at least 620. FHA loans, which are backed by the Federal Housing Administration, may go as low as 580, but the interest rate will be higher and you'll pay mortgage insurance premiums for the life of the loan. VA loans and USDA loans have different score minimums depending on the lender.

If your score is below 620, most lenders won't offer you a mortgage. Your options then are to wait and build your score, work with a credit counselor to dispute errors on your report, or explore whether you meet the requirements for an FHA loan with a co-borrower who has a stronger score.

The role of your down payment

Your down payment is the cash you put toward the purchase price upfront. The rest is borrowed. A 20 percent down payment is the traditional benchmark because it's large enough that lenders don't require you to pay mortgage insurance. If you put down less than 20 percent, you'll pay private mortgage insurance, or PMI, which is an extra monthly fee that protects the lender if you default.

A larger down payment reduces the loan amount you need to borrow, which lowers your monthly payment and your total interest cost over the life of the loan. It also improves your chances of approval and may get you a better interest rate. However, a down payment doesn't directly increase the size of the loan you can get — it decreases it. What it does do is show the lender you have savings and commitment, which can make them more willing to lend to you at all.

If you have saved 5 percent down, you can still get a mortgage. You'll pay PMI, which typically costs 0.5 to 1.5 percent of the loan amount per year, added to your monthly payment. Some lenders allow down payments as low as 3 percent. Government-backed loans like FHA, VA, and USDA have their own down payment rules and insurance requirements.

Income types and what lenders will count

Lenders count W-2 wages, salary, and hourly income straightforwardly. If you've been at your job for less than two years, they may average your income over that time or ask for a letter from your employer confirming you'll stay. If you're self-employed, a freelancer, or have commission income, lenders want to see two years of tax returns to prove your income is stable. They typically average your income over those two years.

Rental income from a property you own can count toward your income, but only after the lender subtracts 25 percent for expenses and vacancy. Social Security, disability, pension, and alimony can all count, but you'll need documentation showing the income is ongoing. Some lenders will count income from a co-borrower — a spouse, family member, or partner — as long as they're on the loan with you.

Lenders will not count income that's temporary or uncertain. Bonus income usually requires documentation that it's recurring. Gifts for your down payment can come from family, but the lender will ask for a letter stating it's a gift, not a loan you have to repay.

Loan types and how they change your borrowing power

A conventional loan is a mortgage not backed by the government. These typically require a credit score of 620 or higher, a down payment of at least 3 to 5 percent, and a debt-to-income ratio under 43 percent. Interest rates are competitive, and you can avoid mortgage insurance with a 20 percent down payment.

An FHA loan is backed by the Federal Housing Administration and allows a credit score as low as 580, a down payment as low as 3.5 percent, and a debt-to-income ratio up to 50 percent in some cases. The tradeoff is that you'll pay mortgage insurance for the life of the loan, which increases your monthly payment. FHA loans are often the path for first-time buyers with lower scores or smaller down payments.

A VA loan is for military members, veterans, and surviving spouses and requires no down payment and no mortgage insurance. The credit score requirement varies by lender but is often more flexible than conventional loans. A USDA loan is for rural homebuyers and also requires no down payment. Both VA and USDA loans have income limits and property location requirements.

What happens after pre-approval

Once you're pre-approved, you have a loan amount you can shop with. When you find a house and make an offer, the lender will order an appraisal to confirm the property is worth what you're paying. If the appraisal comes in lower, the lender may reduce your loan amount, which means you'd need to cover the difference with cash or renegotiate the price.

The lender will also do a final verification of your employment and finances a few days before closing. If you've changed jobs, taken on new debt, or had a significant drop in income, the lender can back out or reduce the loan amount. This is why it's important not to make large purchases or open new credit accounts between pre-approval and closing.

The underwriting process — where the lender reviews all your documents in detail — typically takes 3 to 7 days. During this time, the underwriter may ask for additional documents or explanations. Once underwriting is clear, you move to the final walkthrough and closing, where you sign the paperwork and receive the keys.

Frequently Asked Questions

Can I get a bigger mortgage if I have a co-borrower?

Yes. A co-borrower's income is added to yours when calculating how much you can borrow. Both of your debts count toward the debt-to-income ratio, and both of your credit scores matter. A co-borrower with strong income and a good score can increase your borrowing power significantly, but they're equally responsible for the loan if you default.

What if my debt-to-income ratio is too high?

You can lower it by paying down existing debts before you apply for a mortgage. Paying off a car loan or credit card balance reduces your monthly debt obligations and frees up room in your ratio for a larger mortgage payment. You can also increase your income or wait until your income rises, though lenders need to see the increase documented.

Does the mortgage amount change if I choose a 15-year loan instead of 30 years?

Yes, it usually decreases. A 15-year loan has a higher monthly payment for the same loan amount, which means your debt-to-income ratio climbs faster. You may only may have access to for a smaller loan amount because your income can't support the higher payment. However, a 15-year loan builds equity faster and costs less in total interest.

What if I'm self-employed or have irregular income?

Lenders want to see two years of tax returns to average your income and confirm it's stable. If your income has grown significantly, they may use the most recent year. If it's declined, they'll use the lower figure. Some lenders require a CPA letter confirming your income. Self-employed borrowers often face stricter scrutiny and may need a larger down payment or higher credit score.

Can I increase my mortgage amount after pre-approval?

You can ask the lender to re-evaluate if your financial situation has improved — a raise, a bonus, or paying off a debt. The lender will verify the change and may offer a higher pre-approval amount. However, if your situation has worsened, the lender may reduce the amount. Any significant change requires new documentation and verification.