Your monthly payment depends on three things: the interest rate, the loan term, and how much you put down
A $400,000 mortgage does not have one payment. The same loan amount costs $1,910 per month at 3% interest over 30 years, but $2,280 per month at 6% interest over the same term. If you shorten the loan to 15 years at 6%, the payment jumps to $2,998. The difference between the lowest and highest of those three scenarios is over $1,000 a month—$12,000 a year.
This section shows you how to calculate what you would actually pay, using real numbers for the rates and terms that exist right now. The math is straightforward once you know what moves the needle.
Key Takeaways
- A $400,000 mortgage at 6% interest over 30 years costs approximately $2,280 per month in principal and interest alone.
- Interest rates vary by lender, credit score, and market conditions, so the same loan amount costs different amounts at different times.
- Shortening the loan term from 30 years to 15 years raises the monthly payment by roughly 30 to 40 percent but cuts total interest paid nearly in half.
- Property taxes, homeowners insurance, and mortgage insurance (if your down payment is less than 20 percent) add to the base payment and vary by location and loan details.
- You can use a mortgage calculator with current rates from your lender to see the exact payment for your situation.
How interest rate changes the monthly payment
Interest rate is the single biggest lever on your payment. Here is what $400,000 costs over 30 years at different rates:
| Interest Rate | Monthly Payment (Principal + Interest) | Total Interest Paid Over 30 Years |
|---|---|---|
| 3.0% | $1,910 | $287,600 |
| 4.0% | $1,910 | $287,600 |
| 5.0% | $2,147 | $373,000 |
| 6.0% | $2,398 | $463,200 |
| 7.0% | $2,661 | $557,800 |
A one-percentage-point jump in rate costs you roughly $250 to $300 more per month. Over 30 years, that small monthly difference adds up to tens of thousands of dollars in extra interest.
Your rate depends on the lender you choose, your credit score, the size of your down payment, and current market conditions. Rates change daily. If you are shopping for a mortgage, get quotes from at least three lenders to see the actual rates available to you.
How loan term changes the monthly payment
A 15-year mortgage costs more per month but you pay far less interest overall. Here is the same $400,000 loan at 6% interest, comparing 15-year and 30-year terms:
| Loan Term | Monthly Payment (Principal + Interest) | Total Interest Paid |
|---|---|---|
| 15 years | $2,998 | $139,640 |
| 30 years | $2,398 | $463,200 |
The 15-year payment is $600 higher each month, but you pay $323,560 less in total interest and own the house free and clear 15 years sooner. Whether that trade-off makes sense depends on your cash flow—whether you can afford the higher payment without cutting into savings or other financial goals.
Some people choose a 30-year loan for the lower payment, then pay extra toward principal when they can. Others refinance from 30 years to 15 years after a few years when their income rises. There is no single right answer; it depends on your situation.
What gets added on top of the base payment
The numbers above show principal and interest only. Your actual monthly payment usually includes three other costs: property taxes, homeowners insurance, and possibly mortgage insurance.
Property taxes vary wildly by location. A $400,000 house in one county might have annual property taxes of $4,000, while the same house in another state costs $8,000 or more per year. Your lender will estimate this and add it to your monthly payment. Ask your local assessor's office or a real estate agent what the tax rate is in the area where you are buying.
Homeowners insurance protects the lender's investment if the house burns down or is damaged. Costs vary by the age and condition of the house, your location (hurricane zones and high-crime areas cost more), and the insurance company. A typical range is $100 to $200 per month, but get quotes from insurers in your area for a real number.
Mortgage insurance (PMI) is required if your down payment is less than 20 percent. On a $400,000 house, that means if you put down less than $80,000, you pay PMI. The cost is usually 0.5 to 1.5 percent of the loan amount per year, added to your monthly payment. PMI drops off once you reach 20 percent equity, either through payments or home appreciation.
A real example: what you would actually pay
Say you are buying a $400,000 house, putting down $80,000 (20 percent), and borrowing $320,000. Your rate is 6 percent over 30 years. Here is what your monthly payment looks like:
| Item | Monthly Cost |
|---|---|
| Principal and interest | $1,919 |
| Property tax (estimated) | $350 |
| Homeowners insurance | $150 |
| Mortgage insurance | $0 (20% down) |
| Total monthly payment | $2,419 |
This is what you would see on your mortgage statement. The property tax and insurance amounts are estimates; your actual costs depend on your location and the specific house. The lender collects all three and holds the tax and insurance money in an escrow account, paying those bills on your behalf when they are due.
How to calculate your own payment
You can do this three ways: use an online mortgage calculator, ask a lender directly, or do the math yourself if you want to understand the formula.
An online calculator (search "mortgage calculator") takes your loan amount, interest rate, and term, and shows you the monthly payment when ready. The result is accurate for principal and interest, though you still need to add property tax and insurance separately.
A lender will give you a more complete picture. When you contact a mortgage company or bank, they can quote you a rate based on your credit and down payment, then show you the full monthly payment including taxes and insurance estimates for the specific property.
If you want to calculate it yourself, the formula is: M = P [ r(1+r)^n ] / [ (1+r)^n – 1 ], where M is the monthly payment, P is the loan amount, r is the monthly interest rate (annual rate divided by 12), and n is the number of payments. For a $320,000 loan at 6 percent over 30 years, that works out to $1,919 per month. Most people use a calculator instead of doing this by hand.
Why the same loan amount costs different amounts at different times
Interest rates move based on the Federal Reserve's decisions, inflation, and market demand for mortgages. When rates are low (3 to 4 percent), the same $400,000 loan costs hundreds of dollars less per month than when rates are high (6 to 7 percent). This is why timing matters: buying when rates drop can save you tens of thousands of dollars over the life of the loan.
You cannot control the overall rate environment, but you can control which lender you use and whether you lock in a rate. When you get a quote, the lender will hold that rate for a set number of days (usually 30 to 45) while you shop and make an offer. If rates drop during that time, you can often get a lower rate. If rates rise, you are protected by the lock.
Frequently Asked Questions
What is the monthly payment on a $400,000 mortgage at today's rates?
Rates change daily and vary by lender and your credit profile. Check current rates from at least three lenders (banks, credit unions, online mortgage companies) to see what you would actually pay. Most lenders show rates on their websites or will quote you over the phone in minutes.
Does a larger down payment lower the monthly payment?
Yes. A larger down payment means you borrow less money, so the principal and interest payment is lower. A $80,000 down payment on a $400,000 house means borrowing $320,000; a $100,000 down payment means borrowing $300,000. The second scenario has a lower monthly payment and no mortgage insurance.
Can I pay off a 30-year mortgage early without a penalty?
Most mortgages allow you to pay extra toward principal at any time without penalty. If you make one extra payment per year, or pay $200 extra per month, you shorten the loan term and save on interest. Check your loan documents or ask your lender whether there are any prepayment penalties (rare on modern mortgages, but worth confirming).
What happens to my payment if interest rates drop after I lock in my rate?
Your payment stays the same unless you refinance. Refinancing means taking out a new loan at the lower rate to pay off the old one. You pay closing costs again (usually 2 to 5 percent of the loan amount), so refinancing only makes sense if the rate drop is large enough and you plan to stay in the house long enough to recoup those costs.
Is the monthly payment the only cost of owning a mortgage?
The monthly payment covers principal, interest, taxes, and insurance. You also pay closing costs upfront (typically 2 to 5 percent of the loan amount) and ongoing costs like maintenance, repairs, and utilities. Budget for these separately from the mortgage payment itself.