Your monthly payment depends on three things: the loan amount, the interest rate, and how long you borrow

On a $400,000 house, your monthly payment is not a fixed number. It swings based on your down payment, your interest rate, and your loan term. If you put 20% down ($80,000), borrow $320,000 at 7% interest over 30 years, your principal and interest payment alone is roughly $2,130 per month. But that is only the mortgage itself—not taxes, insurance, or fees.

The real monthly cost to you includes property taxes, homeowners insurance, and possibly mortgage insurance or HOA fees. These vary wildly by location and your specific situation. A $400,000 house in rural Kansas costs far less to own monthly than the same house in suburban Boston or San Francisco.

This section shows you what changes the payment and how to think about each piece.

Key Takeaways

  • Principal and interest on a $320,000 loan (20% down) at 7% over 30 years is about $2,130 per month, but this is only the mortgage itself.
  • Property taxes, homeowners insurance, and mortgage insurance can add $600 to $1,500 or more to your monthly cost, depending on location and your down payment.
  • A smaller down payment (less than 20%) triggers mortgage insurance, which adds roughly $150 to $400 per month until you reach 20% equity.
  • Interest rates change the payment significantly: a 1% difference on a $320,000 loan changes your monthly payment by about $280.
  • Your actual monthly cost depends on your state, county, home value, and insurance market—not just the loan amount.

How down payment size changes what you owe each month

The more you put down, the less you borrow, and the lower your monthly payment. On a $400,000 house, a 20% down payment ($80,000) means you borrow $320,000. A 10% down payment ($40,000) means you borrow $360,000. That extra $40,000 in borrowing adds roughly $265 per month to your principal and interest payment alone.

Down payments below 20% also trigger private mortgage insurance (PMI), which protects the lender if you stop paying. PMI typically costs 0.5% to 1.5% of your loan amount per year, paid monthly. On a $360,000 loan, that is $150 to $450 per month. PMI drops off once you reach 20% equity in the home, either through payments or home appreciation—but that takes years.

A 5% down payment ($20,000) on a $400,000 house means borrowing $380,000 and paying PMI on top. Your principal and interest alone jumps to roughly $2,530 per month, plus PMI of $190 to $570 per month. The total mortgage payment is now $2,720 to $3,100 before taxes and insurance.

Interest rates move your payment up or down by hundreds of dollars

Interest rates change almost daily. A 6.5% rate versus a 7.5% rate on a $320,000 loan over 30 years is a difference of about $210 per month. Over the life of the loan, that is $75,600 in extra interest paid.

Rates depend on the lender, the loan type (conventional, FHA, VA), your credit score, and current market conditions. A borrower with a 750+ credit score typically gets a lower rate than one with a 650 score. An FHA loan (which allows 3.5% down) usually carries a higher rate than a conventional loan. A VA loan (for military) often carries the lowest rates available.

When you shop for a mortgage, ask each lender for the rate and the annual percentage rate (APR), which includes fees. The APR is the true cost of borrowing and lets you compare lenders fairly.

Property taxes and insurance add hundreds to your monthly bill

Property taxes vary by state and county. New Jersey and Illinois have high property taxes; Alabama and Louisiana have low ones. On a $400,000 house, annual property taxes might be $3,000 in a low-tax state or $12,000 in a high-tax state. That is $250 to $1,000 per month, paid as part of your mortgage payment into an escrow account.

Homeowners insurance covers fire, theft, and liability. On a $400,000 house, annual premiums typically range from $1,200 to $2,400, or $100 to $200 per month. Rates depend on the home's age, construction, location, and your claims history. Homes in flood zones or hurricane-prone areas cost significantly more to insure.

Your lender requires both taxes and insurance to be paid before the mortgage itself. If you do not pay them, the lender can pay them on your behalf and add the cost to your loan balance—which means you pay interest on the taxes and insurance too.

How to calculate your total monthly payment

Use this breakdown to estimate your own cost. Start with your loan amount (house price minus down payment), your interest rate, and your loan term. A mortgage calculator will give you principal and interest. Then add:

  • Property tax: Find your county assessor's website and look up the tax rate. Multiply the house price by that rate and divide by 12.
  • Homeowners insurance: Call three insurers for quotes. Average them and divide by 12.
  • Mortgage insurance (if down payment is less than 20%): Ask the lender for the monthly PMI amount.
  • HOA fees (if applicable): Ask the seller or real estate agent for the monthly amount.

Add all four numbers together. That is your total monthly housing payment. On a $400,000 house with 20% down at 7% interest in a moderate-tax state, expect $2,800 to $3,500 per month. In a high-tax state or with a smaller down payment, expect $3,500 to $4,500 per month.

What happens if interest rates drop after you lock in

Once you close on a mortgage, your rate is fixed (assuming a fixed-rate loan). If rates drop later, you can refinance—take out a new loan to pay off the old one. Refinancing costs $2,000 to $5,000 in fees, so it only makes sense if rates drop by at least 0.5% to 1% and you plan to stay in the home long enough to recoup the fees.

If rates rise after you lock in, you are protected. Your payment stays the same for the life of the loan (on a fixed-rate mortgage). This is why locking in your rate before closing matters.

Frequently Asked Questions

Can I afford a $400,000 house on my income?

Lenders typically allow your total monthly housing payment (mortgage, taxes, insurance, HOA) to be no more than 28% of your gross monthly income. If your housing payment is $3,500, you need a gross income of about $12,500 per month, or $150,000 per year. Some lenders go up to 43% of gross income if your other debts are low.

What is the difference between a 15-year and 30-year mortgage?

A 15-year mortgage has a higher monthly payment but you pay far less interest overall. On a $320,000 loan at 7%, a 15-year payment is roughly $3,000 per month versus $2,130 for 30 years. Over the life of the loan, you pay about $220,000 less in interest with the 15-year option, but your monthly cash flow is tighter.

Does my credit score affect the interest rate I get?

Yes. A credit score of 760+ typically gets the lowest available rate. A score of 700–759 might be 0.25% to 0.5% higher. Below 700, the rate jumps further. On a $320,000 loan, a 0.5% rate difference is about $170 per month, so a higher credit score saves real money.

What if I want to pay off the mortgage faster?

You can make extra payments toward principal without penalty on most mortgages. Paying an extra $200 per month on a 30-year loan cuts years off the term and saves tens of thousands in interest. Ask your lender how to make sure extra payments go to principal, not the next month's payment.

Do I have to pay property taxes and insurance every month?

Your lender requires them to be paid before the mortgage itself. Most lenders collect taxes and insurance through an escrow account—you pay them monthly as part of your mortgage payment, and the lender pays the bills when they are due. Some lenders allow you to pay taxes and insurance separately if you have significant equity in the home.