Your monthly payment depends on three things: the interest rate, how many years you borrow for, and whether you have a fixed or adjustable rate
A $400,000 mortgage at 7% interest over 30 years costs roughly $2,660 per month in principal and interest alone. At 6%, the same loan costs about $2,400 per month. At 8%, it rises to about $2,935 per month. These numbers shift based on your interest rate and loan term — a 15-year mortgage costs more each month but less in total interest paid over time.
The monthly payment you actually send your lender will be higher than these figures because it includes property taxes, homeowners insurance, and possibly mortgage insurance. These costs vary by location and your down payment size, so your true monthly obligation could be $3,200 to $3,800 or more depending on where you live and what you put down.
Key Takeaways
- A $400,000 mortgage at 7% interest over 30 years costs about $2,660 per month in principal and interest, before taxes and insurance.
- Each 1% change in interest rate shifts your monthly payment by roughly $250 to $300 on a 30-year loan.
- Choosing a 15-year loan instead of 30 years nearly doubles your monthly payment but cuts your total interest cost in half.
- Your actual monthly bill includes property taxes, homeowners insurance, and possibly private mortgage insurance, which can add $500 to $1,200 or more depending on location and down payment.
How interest rate changes affect your monthly payment
Interest rates move constantly, and even a small shift changes what you owe each month. The table below shows how a $400,000 mortgage over 30 years changes as the rate moves:
| Interest Rate | Monthly Payment (Principal & Interest) |
|---|---|
| 5.5% | ~$2,271 |
| 6.0% | ~$2,399 |
| 6.5% | ~$2,531 |
| 7.0% | ~$2,661 |
| 7.5% | ~$2,797 |
| 8.0% | ~$2,935 |
These are estimates based on standard loan math. Your actual rate depends on your credit score, down payment size, loan type, and current market conditions. A lender will give you a precise quote once you provide your financial information.
The difference between a 30-year and 15-year mortgage
A 15-year mortgage lets you pay off the house faster and costs far less in total interest, but your monthly payment is significantly higher. On a $400,000 loan at 7% interest, a 15-year mortgage costs about $3,990 per month compared to $2,661 for a 30-year loan — roughly $1,330 more each month.
Over the life of the loan, the 15-year mortgage saves you around $350,000 in interest. The 30-year mortgage spreads payments over twice as long, so you pay less monthly but much more in total interest. Choose based on what your budget can handle now, not what sounds better in theory. If the higher payment would strain your finances, the 30-year option is the right choice.
What gets added to your principal and interest payment
Your lender bundles several costs into one monthly bill. Property taxes vary widely by state and county — some areas charge 0.5% of home value yearly, others charge 2% or more. On a $400,000 home, that could be $2,000 to $8,000 per year, or $167 to $667 per month.
Homeowners insurance typically costs $800 to $2,000 per year depending on the home's age, location, and what coverage you choose. That works out to roughly $67 to $167 per month. If you put down less than 20%, your lender requires private mortgage insurance (PMI), which protects the lender if you stop paying. PMI on a $400,000 loan usually runs $200 to $400 per month, though it drops off once you reach 20% equity in the home.
Add these together and your total monthly payment could easily be $3,200 to $3,800 before you account for homeowners association fees, if your property has them. This is why lenders look at your income — they want to see that your housing costs don't exceed 28% to 31% of your gross monthly income.
How your down payment affects the monthly cost
The size of your down payment changes both the loan amount and whether you pay PMI. If you put down 20% ($80,000), you borrow $320,000 instead of $400,000, and you avoid PMI entirely. If you put down 10% ($40,000), you borrow $360,000 and pay PMI until you reach 20% equity.
A smaller down payment means a lower upfront cost but a higher monthly payment and the added expense of PMI. A larger down payment means less to borrow and no PMI, but you need more cash on hand before closing. Most people balance these by putting down 10% to 20% and accepting PMI for a few years if needed.
Fixed-rate versus adjustable-rate mortgages
A fixed-rate mortgage locks in one interest rate for the entire loan term — 30 years, 15 years, or whatever you choose. Your monthly payment never changes. This makes budgeting predictable and protects you if rates rise.
An adjustable-rate mortgage (ARM) starts with a lower rate for a set period (often 3, 5, 7, or 10 years), then adjusts annually based on market conditions. Your payment might be $2,400 for the first 5 years, then jump to $2,800 or higher when the adjustment period ends. ARMs are riskier because you cannot predict your payment after the initial period. Most first-time buyers choose fixed-rate mortgages because the predictability matters more than the small initial savings.
Using a mortgage calculator to estimate your own payment
The figures in this guide are estimates. Your actual payment depends on your specific interest rate, loan term, property location, insurance costs, and down payment size. Most lenders and financial websites offer free mortgage calculators where you enter your numbers and see the exact monthly payment.
When you use a calculator, you will need to know or estimate: the loan amount, the interest rate (ask your lender for a rate quote), the loan term in years, your property tax rate (your real estate agent or county assessor can tell you), and your estimated homeowners insurance cost (call an insurance agent for a quote). Plugging in real numbers gives you a far more accurate picture than any general example.
Frequently Asked Questions
Does the monthly payment include property taxes and insurance?
It depends on your loan type. Most mortgages use an escrow account, where your lender collects property taxes and insurance as part of your monthly payment, then pays those bills on your behalf. Some loans do not require this, and you pay taxes and insurance separately. Ask your lender whether escrow is included in the quoted payment.
What happens to my payment if interest rates drop after I lock in my rate?
Your payment stays the same if you have a fixed-rate mortgage — that is the whole point of locking in a rate. You could refinance to a lower rate later, which would lower your payment, but refinancing costs money upfront and resets your loan term. Refinancing makes sense only if the rate drop is large enough to offset those costs.
Can I pay extra toward principal each month?
Yes. Most mortgages allow you to pay extra without penalty. Any amount above your required monthly payment goes directly to principal, which shortens your loan term and saves interest. Even an extra $100 or $200 per month adds up over time, but only do this if your budget comfortably allows it.
What if I cannot afford the monthly payment I calculated?
A $400,000 mortgage may not be the right loan amount for your income. Lenders typically want housing costs to be no more than 28% to 31% of your gross monthly income. If the payment exceeds that, consider a smaller loan amount, a larger down payment, or waiting until your income increases. A mortgage broker can help you find what loan amount fits your budget.