Your monthly payment depends on three things: the interest rate, the loan term, and whether you have an adjustable or fixed rate

On a $400,000 mortgage, your monthly payment (principal and interest only) ranges from roughly $1,900 to $2,900, depending on the rate and term you lock in. A 30-year fixed mortgage at 7% costs about $2,660 per month. The same loan at 6% costs about $2,400. At 5%, it drops to roughly $2,150. These numbers shift with every change in rate and every year you add or subtract from the loan term.

The payment you see quoted never includes property taxes, homeowners insurance, or mortgage insurance (if your down payment was less than 20%). Those costs stack on top and vary by location and your specific situation. A lender will show you the full monthly obligation — called PITI (principal, interest, taxes, insurance) — before you commit.

Key Takeaways

  • A $400,000 mortgage at 7% over 30 years costs about $2,660 per month in principal and interest alone.
  • Lowering the interest rate by 1% cuts your monthly payment by roughly $250 to $300.
  • Shortening the loan term to 15 years raises the monthly payment but cuts total interest paid nearly in half.
  • Your actual monthly bill includes taxes, insurance, and possibly mortgage insurance on top of the base payment.
  • Locking in a rate now protects you from future increases, but rates vary daily and by lender.

How interest rate changes affect your payment

The interest rate is the single biggest lever on your monthly cost. A difference of 0.5% on a $400,000 loan over 30 years changes your payment by roughly $100 to $150 per month. A full 1% difference swings it by $250 to $300.

Rates move daily based on the bond market, the Federal Reserve's actions, and lender competition. When you get a quote, ask whether it includes a rate lock — a may provide that the rate stays the same for a set number of days (usually 30 to 60). Without a lock, the rate can change before closing. With a lock, you pay a small fee to protect yourself, but you know exactly what you owe.

If you are considering an adjustable-rate mortgage (ARM), the initial rate is lower — sometimes 0.5% to 1% below a fixed rate — but it resets after a set period (often 5, 7, or 10 years). When it resets, your payment can jump by $300 to $500 or more per month. ARMs make sense only if you plan to sell or refinance before the rate adjusts, or if you can absorb a payment increase later.

The difference between a 15-year and 30-year loan

A 15-year mortgage on $400,000 at 7% costs about $3,990 per month — roughly $1,330 more than the 30-year version. Over the life of the loan, you pay far less interest: about $120,000 total on the 15-year versus $360,000 on the 30-year. That is a savings of $240,000.

The trade-off is simple: higher monthly payment now, or lower payment spread over twice as long. Most people choose the 30-year because it leaves more room in their monthly budget for other expenses and emergencies. But if you can afford the 15-year payment and plan to stay in the home, you build equity faster and pay off the debt sooner.

Some borrowers split the difference with a 20-year loan, which costs roughly $3,200 per month on the same terms. There is no single right answer — it depends on your income, other debts, and how long you plan to own the home.

What gets added to your base payment

The $2,660 monthly payment at 7% covers only principal and interest. Your actual bill from the lender includes property taxes and homeowners insurance, which vary widely by location. In a high-tax area like New Jersey or New York, taxes alone can add $400 to $800 per month. In a low-tax state like Texas or Florida, they might add $150 to $300.

If your down payment was less than 20% of the home price — meaning you borrowed more than $320,000 on a $400,000 home — you also pay private mortgage insurance (PMI). PMI typically costs 0.5% to 1.5% of the loan amount per year, divided into monthly payments. On a $400,000 loan, that is $167 to $500 per month until you reach 20% equity. Once you hit that threshold, you can request PMI removal.

Homeowners association (HOA) fees, if your property has them, are separate and not part of the mortgage payment. Ask your lender for a Loan Estimate, which breaks down every cost you will owe at closing and every monthly charge going forward.

How to compare offers from different lenders

Lenders quote different rates and fees, so comparing three to five offers is worth the time. Request a Loan Estimate from each lender within the same day or two, so the rates are roughly comparable. The Loan Estimate shows the interest rate, the APR (which includes fees), the monthly payment, and closing costs.

Do not compare based on rate alone. A lender with a 6.9% rate but $5,000 in fees may cost you more over time than one with a 7.1% rate and $2,000 in fees. Use an online mortgage calculator to run the numbers: plug in the rate, the loan amount, the term, and the fees, and see which lender's total cost is lowest over 5, 10, and 30 years.

Ask each lender whether the rate is locked and for how long. Some lenders offer a "float-down" option, which lets you lock in a lower rate if rates drop before closing — usually for a fee of 0.25% to 0.5% of the loan amount. If rates are expected to fall, this can be worth the cost.

How much house you can actually afford

A $400,000 mortgage assumes you have already decided on that price. But lenders use debt-to-income ratio (DTI) to decide how much they will lend you. Most lenders cap your total monthly debt payments — including the mortgage, car loans, credit cards, and student loans — at 43% to 50% of your gross monthly income.

If your gross income is $8,000 per month and you have no other debt, a lender might approve you for a $400,000 mortgage. But if you have $1,500 in car and student loan payments, that same lender might cap you at $250,000 to $300,000, because the total debt would exceed their DTI limit.

Before you start house hunting, get pre-approved by a lender. Pre-approval tells you the maximum loan amount you may have access to for based on your income, credit, and existing debts. It is different from pre-qualification, which is just a rough estimate. Pre-approval carries weight with sellers and takes the guesswork out of your budget.

What happens if rates drop after you lock in

If you lock in a 7% rate and rates fall to 6.5% before closing, you are stuck at 7% — that is the point of a lock. You cannot change your mind without breaking the lock, which usually costs a fee or means losing your rate protection.

Some lenders offer a one-time rate reduction, which lets you lower your rate once if it falls during the lock period. This costs extra upfront but protects you if the market moves in your favor. If rates are falling and you expect them to keep falling, ask your lender about this option.

If you close and then rates drop significantly, you can refinance — take out a new loan at the lower rate to pay off the old one. Refinancing costs money (closing costs again), so it only makes sense if the rate drop is large enough and you plan to stay in the home long enough to recoup those costs. A general rule: refinance if the new rate is at least 0.5% lower than your current rate.

Frequently Asked Questions

What is the difference between APR and interest rate?

The interest rate is what you pay to borrow the money. The APR (annual percentage rate) includes the interest rate plus lender fees, spread across the loan term. APR is always equal to or higher than the interest rate. Use APR to compare offers from different lenders, because it shows the true cost of borrowing.

Can I pay off my mortgage early without a penalty?

Most mortgages have no prepayment penalty, meaning you can pay extra toward principal anytime without a fee. Paying an extra $100 or $200 per month cuts years off the loan and saves tens of thousands in interest. Check your loan documents or ask your lender to confirm there is no penalty.

What credit score do I need to get approved for a $400,000 mortgage?

Most lenders require a credit score of at least 620 to 640 for a conventional mortgage, but scores of 740 and above get the best rates. FHA loans (backed by the Federal Housing Administration) accept scores as low as 580. The higher your score, the lower your rate, so even a 20-point improvement can save you thousands over the life of the loan.

How much should I put down on a $400,000 home?

The minimum is typically 3% to 5% for a conventional loan ($12,000 to $20,000), but putting down 20% ($80,000) eliminates PMI and lowers your rate. If you have less than 20% saved, you can still buy — you will just pay PMI until you reach 20% equity. Some buyers put down 10% to 15% as a middle ground.

What if I want to lock in a rate but rates are expected to rise?

Lock immediately. Locking protects you from future increases during the lock period. If rates rise after you lock, you keep your rate. If rates fall, you can ask about a rate reduction option (if your lender offers it) or refinance later. Locking costs nothing — you only pay if you break the lock before closing.