What lenders look at when you ask for a mortgage
A lender will not hand you a mortgage amount based on what you want to spend. They calculate how much they believe you can repay by looking at your income, debts, credit history, and the down payment you have saved. The largest mortgage you can get is usually limited by one of two calculations: either the amount your income supports, or the amount the home itself is worth. Whichever is smaller is what you will be offered.
The income-based limit is what most people hit first. Lenders use a debt-to-income ratio — a comparison of your monthly debt payments to your gross monthly income. Most conventional lenders will not go above 43 percent, meaning if you earn $5,000 a month before taxes, your total monthly debt (including the new mortgage payment) cannot exceed about $2,150. Some lenders will stretch to 50 percent for borrowers with strong credit and savings, but this is less common.
Your credit score affects both whether you get approved and what interest rate you pay. A score of 620 or higher typically opens the door to a mortgage, but scores below 740 usually mean a higher rate, which makes the same loan more expensive each month. A higher rate also reduces how much you can borrow, because the monthly payment on that larger amount would push you over your debt-to-income limit.
Key Takeaways
- Lenders calculate your maximum mortgage using your gross monthly income and existing debts, typically allowing a mortgage payment that does not exceed 43 percent of what you earn before taxes.
- Your credit score determines whether you get approved and what interest rate you receive, which directly affects how large a loan you can afford.
- The down payment you have saved limits the mortgage amount because lenders will not lend more than the home is worth.
- A mortgage pre-qualification letter from a lender shows you a realistic borrowing range based on your actual finances, not an estimate from an online calculator.
- Paying down existing debts before you apply increases the mortgage amount you can borrow without changing your income.
How your down payment affects your borrowing limit
The amount you have saved for a down payment directly controls the size of the mortgage you can take. If a home is worth $300,000 and you have $60,000 saved (20 percent down), the lender will not lend you more than $240,000 for that property. If you only have $30,000 saved (10 percent down), the maximum mortgage for that same home is $270,000.
A smaller down payment also triggers mortgage insurance, an extra monthly cost that protects the lender if you stop paying. This insurance is added to your monthly payment, which means it counts toward your debt-to-income ratio. A 10 percent down payment typically costs 0.5 to 1 percent of the loan amount per year, spread across your monthly payments. This extra cost reduces how much total house you can afford, because the payment is higher for the same loan size.
Saving a larger down payment before you apply is one of the clearest ways to increase your borrowing power. Moving from 5 percent down to 15 percent down removes the mortgage insurance requirement entirely and reduces your monthly payment, freeing up room in your debt-to-income ratio for a larger loan.
How existing debts reduce what you can borrow
Every monthly debt payment you currently make — car loans, student loans, credit cards, personal loans, child support — counts against your debt-to-income ratio. If you owe $400 a month on a car and $200 a month on student loans, that is $600 already subtracted from the mortgage payment your income can support.
This is why paying down debts before you apply for a mortgage can increase your borrowing power without any change to your income. If you eliminate that $400 car payment, you free up $400 of monthly debt capacity. On a 30-year mortgage at typical interest rates, that $400 a month translates to roughly $80,000 to $100,000 in additional borrowing power.
Credit card balances count even if you pay them in full each month. Lenders use the card's credit limit or your highest recent balance — whichever is higher — to estimate a potential monthly payment, usually calculated as 2 to 5 percent of the balance. Paying down credit card debt before you apply has the same effect as paying off a car loan: it increases your available debt capacity.
The difference between pre-qualification and pre-approval
A pre-qualification is an estimate a lender gives you based on information you provide over the phone or online. It is not a promise. The lender has not verified your income, checked your credit, or reviewed your assets. It is useful for understanding a rough range, but it can change significantly once the lender actually looks at your finances.
A pre-approval is a formal offer based on documents you have submitted: recent pay stubs, tax returns, bank statements, and a credit report the lender has pulled themselves. The lender has verified that the income and assets you described are real. A pre-approval letter states a specific mortgage amount you can borrow, though the final approval still depends on the home passing an appraisal and your financial situation not changing before closing.
If you are serious about buying, get a pre-approval before you start looking at homes. It shows sellers you are a real buyer, and it gives you an accurate picture of what you can actually borrow rather than a guess.
Why the home's value sets a ceiling on your loan
Even if your income supports a $400,000 mortgage, a lender will not lend you $400,000 to buy a $300,000 home. The mortgage is secured by the house itself — if you stop paying, the lender takes the house and sells it to recover the loan. A lender will not lend more than the home is worth because they would lose money in a foreclosure.
This is why the appraisal matters. Before closing, the lender orders an independent appraisal to confirm the home is worth what you agreed to pay. If the appraisal comes in lower than the purchase price, the lender will reduce the mortgage amount to match the appraised value. You then have to make up the difference with a larger down payment, renegotiate the price with the seller, or walk away from the deal.
In a hot market where homes sell quickly, appraisals sometimes come in lower than expected. This is one reason to have savings beyond your down payment — to cover the gap if the appraisal does not support the purchase price.
How interest rates change what you can borrow
Interest rates move constantly, and even a small change affects how much you can borrow. A higher interest rate means a larger monthly payment on the same loan size, which pushes you closer to or over your debt-to-income limit. A lower rate means a smaller monthly payment, freeing up room to borrow more.
For example, a $300,000 mortgage at 6 percent interest costs about $1,799 per month (principal and interest only). The same $300,000 at 7 percent costs about $1,996 per month — nearly $200 more. That $200 difference counts against your debt-to-income ratio. If you are already near your limit, a rate increase of one percentage point could reduce the mortgage amount you can borrow by $50,000 or more.
You cannot control interest rates, but you can control your credit score and down payment, both of which affect the rate you receive. A higher credit score and a larger down payment usually mean a lower rate, which increases your borrowing power.
What happens after you know your maximum
Knowing the largest mortgage you can borrow is not the same as knowing what you should borrow. A lender will tell you the maximum based on your debt-to-income ratio, but that maximum assumes you are comfortable spending 43 percent of your gross income on housing and debt. Many financial advisors suggest keeping housing costs to 28 percent of gross income or less, which would be a smaller mortgage than your lender offers.
The difference between what you can borrow and what you should borrow is personal. It depends on your job stability, whether you have an emergency fund, how much you value financial flexibility, and what other financial goals matter to you. A pre-approval letter tells you the lender's limit. Your own budget tells you what makes sense for your life.
Frequently Asked Questions
Can I get a mortgage with a credit score below 620?
Some lenders offer mortgages to borrowers with scores as low as 580, but these loans come with higher interest rates and often require a larger down payment. The cost of borrowing is significantly higher, which reduces how much you can afford to borrow. Building your credit score before you apply usually saves you money.
Does a co-signer increase the mortgage I can borrow?
Yes. A co-signer's income and debts are added to yours when calculating your debt-to-income ratio. If a co-signer has strong income and low debt, they can increase your borrowing power. However, the co-signer is legally responsible for the loan if you do not pay, so this is a serious commitment for them.
What if I have a large inheritance or gift coming?
Money you have not yet received does not count toward your down payment or assets. Lenders only count money that is already in your bank account or that you can document is committed to you in writing. Once the money arrives and sits in your account for a set period (usually 30 to 60 days), it counts toward your down payment.
Does being self-employed change how lenders calculate my mortgage?
Yes. Self-employed borrowers must show two years of tax returns to prove income, and lenders average the income across those years. If your income has been growing, this can result in a lower approved mortgage than a W-2 employee with the same current income would receive. Keeping clean financial records and tax returns is essential.
Can I increase my mortgage amount after I get pre-approved?
You can ask your lender to recalculate if your financial situation improves — a raise, paying off a debt, or saving a larger down payment. The lender will re-verify your information and may offer a higher amount. However, if your situation worsens or rates rise significantly, your pre-approval could be reduced or withdrawn.