The payment depends on your down payment, interest rate, and loan term

A $400,000 house does not have one mortgage payment. The actual amount you pay each month depends on three things: how much you put down, what interest rate you lock in, and whether you choose a 15-year or 30-year loan. On the same house, two buyers can have monthly payments that differ by $500 or more.

Here is what moves the number: if you put 20% down on a $400,000 house, you borrow $320,000. If you put 10% down, you borrow $360,000. That $40,000 difference alone changes your payment by roughly $240 a month on a 30-year loan. Interest rates shift constantly—a rate of 6% versus 7% on the same loan size changes your payment by about $150 a month. And a 15-year loan costs roughly twice as much per month as a 30-year loan on the same borrowed amount, because you are paying it back in half the time.

Key Takeaways

  • A $400,000 house with 20% down and a 6% interest rate on a 30-year loan costs roughly $1,440 per month in principal and interest alone.
  • Putting down less than 20% adds mortgage insurance (PMI) to your payment, typically 0.5% to 1% of the loan amount per year.
  • Your actual monthly housing cost includes property taxes, homeowners insurance, and HOA fees on top of the mortgage payment itself.
  • A one percentage point change in interest rate shifts your monthly payment by $150 to $200, so locking in your rate matters.
  • A 15-year loan costs roughly $400 to $500 more per month than a 30-year loan on the same amount borrowed, but you own the house faster and pay far less interest overall.

How the basic payment is calculated

Lenders use a formula that spreads your borrowed amount, interest, and loan term across equal monthly payments. The formula is the same everywhere—what changes is the numbers you plug in. If you borrow $320,000 at 6% interest over 30 years, the monthly payment (principal and interest only) is approximately $1,919. If the same loan is at 7%, it rises to about $2,128. If you borrow $360,000 at 6%, it becomes roughly $2,158.

You can calculate this yourself using an online mortgage calculator, or ask a lender for a loan estimate. The loan estimate is a real document—it shows the exact interest rate, the exact amount borrowed, the exact monthly payment, and all the fees involved. It is free and does not lock you into anything. Getting estimates from two or three lenders takes an hour and can show you the real range of what you will pay.

What happens when you put down less than 20%

If you put down 10% instead of 20%, your monthly payment rises in two ways. First, you are borrowing more money, so the base payment is higher. Second, lenders require mortgage insurance (PMI) when you borrow more than 80% of the home's value. PMI protects the lender if you stop paying; it does not protect you.

PMI typically costs between 0.5% and 1% of your loan amount per year, divided into your monthly payment. On a $360,000 loan, that is $150 to $300 per month added to your mortgage payment. You can remove PMI once you have paid down the loan to 80% of the home's original value, but that takes years. Some lenders let you remove it sooner if your home has gained value and you refinance, but that involves new closing costs.

Property taxes, insurance, and other costs you pay alongside the mortgage

Your mortgage payment covers only principal and interest. Your actual monthly housing cost is higher. Property taxes vary wildly by location—some counties charge 0.5% of home value per year, others charge 2% or more. On a $400,000 house, that is anywhere from $167 to $667 per month. Homeowners insurance typically runs $100 to $300 per month depending on the house and your location. If you have an HOA, add that fee too.

Lenders often roll property taxes and insurance into your monthly payment through an escrow account. You pay the lender, the lender holds the money, and the lender pays the tax bill and insurance bill when they are due. This means your actual monthly payment to the lender is higher than the principal-and-interest number alone. A loan estimate shows this total payment, called the PITI payment (principal, interest, taxes, insurance).

How interest rates affect what you pay over time

Interest rate changes look small on paper but compound into real money. On a $320,000 loan over 30 years, the difference between 5.5% and 7% is about $300 per month. Over 30 years, that is $108,000 in extra payments. Locking in a lower rate saves you tens of thousands of dollars.

Rates change daily and depend on the broader economy, the Federal Reserve's decisions, and the lender's own pricing. You can lock a rate for a set number of days—usually 30, 45, or 60 days—while you shop for a house and complete inspections. If rates drop before you lock, you can often renegotiate. If rates rise after you lock, you are protected. Locking costs nothing, but it does expire, so time it carefully.

15-year versus 30-year loans

A 15-year loan has a higher monthly payment but costs far less in total interest. On a $320,000 loan at 6%, a 30-year payment is roughly $1,919 per month. A 15-year payment on the same loan and rate is roughly $2,697 per month—about $778 more. Over 15 years, you pay roughly $185,460 in total interest on the 15-year loan. Over 30 years on the 30-year loan, you pay roughly $371,000 in total interest. The 15-year loan saves you about $185,000 in interest, but only if you can afford the higher payment.

Most first-time buyers choose a 30-year loan because the payment is lower and leaves room in the budget for other expenses. If you have stable income and want to build equity faster and pay less interest, a 15-year loan is an option. Some buyers do a 30-year loan initially and refinance to a 15-year later, once their income has risen or they have paid down the principal.

Getting a real number from a lender

Online calculators give you a ballpark figure, but a lender's loan estimate gives you the actual number you will pay. To get one, you need to tell the lender the home price, your down payment amount, and your desired loan term. The lender will quote you an interest rate (which may be a sample rate or a rate locked for a short time) and show you the monthly payment, all fees, and the total cost of the loan.

You do not need to commit to anything to get an estimate. Shop with at least two lenders—a bank, a credit union, and a mortgage broker often have different rates and fees. The difference between lenders on the same loan can be $100 to $200 per month, which is real money. Comparing estimates takes a few hours and can save you tens of thousands over the life of the loan.

Frequently Asked Questions

What is the monthly payment on a $400,000 house with 20% down at 6% interest?

With $80,000 down, you borrow $320,000. At 6% interest over 30 years, the principal and interest payment is approximately $1,919 per month. Add property taxes, insurance, and possibly HOA fees to get your total monthly housing cost, which typically ranges from $2,300 to $2,800 depending on location.

How much does PMI add to my payment?

PMI typically costs 0.5% to 1% of your loan amount per year. On a $360,000 loan (10% down on a $400,000 house), that is $150 to $300 per month. You can remove it once you have paid the loan down to 80% of the home's value, which usually takes 5 to 10 years depending on your payments and home appreciation.

Does a lower interest rate really make that much difference?

Yes. On a $320,000 loan, each 0.5% change in interest rate shifts your monthly payment by roughly $75 to $100. Over 30 years, a 0.5% difference costs or saves you about $27,000 in total interest. Shopping for rates across multiple lenders is worth the time.

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 $2,500, you need a gross income of roughly $107,000 per year. This is a guideline, not a rule—some lenders are stricter, others more flexible, depending on your credit and savings.

What if I want to pay off the house faster?

You can make extra payments toward principal at any time without penalty. Some people do a 30-year loan but pay as if it were a 20-year loan, which gives them flexibility if money gets tight. Others refinance from a 30-year to a 15-year loan once their income rises. Both approaches work; the key is making sure the extra payment goes toward principal, not into an escrow account.