Your monthly mortgage payment depends on the loan amount, interest rate, and how many years you have to repay it

A mortgage payment is not just interest. It includes principal (the amount you borrowed), interest (what the lender charges), property taxes, homeowners insurance, and sometimes mortgage insurance if you put down less than 20 percent. The principal and interest portion stays the same every month for a fixed-rate mortgage, but property taxes and insurance can rise over time.

The simplest way to see what you might pay is to use a mortgage calculator — you enter the loan amount, interest rate, and loan term (usually 15 or 30 years), and it shows you the principal-and-interest portion. Then you add your local property tax rate and insurance estimate to get the full picture.

Key Takeaways

  • Principal and interest on a 30-year mortgage at 7 percent interest on a $300,000 loan runs roughly $1,995 per month, but your actual payment will be higher once you add taxes and insurance.
  • A shorter loan term (15 years instead of 30) means a higher monthly payment but you pay far less interest over the life of the loan.
  • Property taxes vary by county and city, so you need to know your local rate to estimate your true monthly cost.
  • Homeowners insurance is required by lenders and typically costs $800 to $2,000 per year, depending on the home value and your location.
  • If you put down less than 20 percent, your lender will add mortgage insurance (PMI) to your payment until you build enough equity.

The formula lenders use to calculate principal and interest

Lenders use a standard formula to divide your monthly payment between principal and interest. Early in the loan, most of your payment goes to interest. As you pay down the principal, more of each payment goes toward the amount you actually borrowed.

You do not need to do the math yourself — a mortgage calculator does it instantly. But the inputs matter: a $400,000 loan at 6.5 percent over 30 years produces a different number than the same loan at 7.5 percent. Even a half-percent difference in interest rate changes your monthly payment by roughly $100 to $150 on a $400,000 loan.

The loan term also shifts the payment significantly. A 15-year mortgage has a higher monthly payment than a 30-year mortgage on the same amount, because you are paying it back in half the time. But you pay much less total interest — sometimes $100,000 or more less over the life of the loan.

Property taxes and insurance add to your base payment

Your lender requires you to pay property taxes and homeowners insurance as part of your monthly mortgage payment. These go into an escrow account that the lender manages, and they pay the tax bill and insurance premium on your behalf when they are due.

Property tax rates vary widely by location. Some counties charge 0.5 percent of home value per year; others charge 1.5 percent or more. A $400,000 home in a 1 percent tax area costs $4,000 per year in property tax alone — roughly $333 per month. In a 0.5 percent area, it is $167 per month. You can find your local rate through your county assessor's office or a tax estimate tool.

Homeowners insurance typically costs $100 to $200 per month, though it varies by home age, location, and whether you live in a flood or hurricane zone. Older homes and homes in high-risk areas cost more to insure. Ask an insurance agent for a quote on the specific property before you lock in your estimate.

Mortgage insurance (PMI) if you put down less than 20 percent

If your down payment is less than 20 percent of the home price, your lender requires private mortgage insurance (PMI). This protects the lender if you default, but you pay the premium — usually 0.5 to 1.5 percent of the loan amount per year, divided into your monthly payment.

On a $400,000 loan with 10 percent down ($40,000), your PMI might run $150 to $400 per month. Once you have paid down the loan to 80 percent of the original home value, you can request to have PMI removed. This usually happens after several years of on-time payments, but the timeline depends on your loan and how fast home values rise in your area.

A real example: what $300,000 actually costs per month

Assume you borrow $300,000 at 7 percent interest over 30 years. Principal and interest run about $1,995 per month. Add $250 per month for property tax (on a home in a 1 percent tax area), $150 per month for homeowners insurance, and $100 per month for PMI (because you put down 15 percent). Your total monthly payment is roughly $2,495.

If you had put down 20 percent instead ($60,000), you would skip the PMI and save $100 per month. If your interest rate had been 6 percent instead of 7 percent, your principal and interest would drop to about $1,799 — a savings of nearly $200 per month. These small differences compound over 30 years.

How to estimate your own payment before you shop for a home

Start with a mortgage calculator and enter three numbers: the loan amount you are considering, the current interest rate (check a mortgage lender's website for today's rates), and the loan term you prefer. This gives you the principal-and-interest portion.

Then add your local property tax rate. Call your county assessor's office or search "[your county] property tax rate" online. Multiply your estimated home price by that rate and divide by 12 to get the monthly amount.

For insurance, contact a homeowners insurance agent and ask for a quote on a home in the price range you are considering. Divide the annual premium by 12 to get the monthly cost. Add all three numbers together, and you have a realistic estimate of what your payment will be.

What changes your payment over time

On a fixed-rate mortgage, your principal-and-interest payment never changes. But property taxes and insurance do. Property taxes usually rise every few years as your county reassesses home values. Insurance premiums climb when insurers raise rates in your area or when you file a claim.

Your lender reviews your escrow account once a year. If taxes and insurance have risen, your monthly payment goes up. If they have fallen (rare), your payment may drop. This is why your actual payment can be higher in year five than it was in year one, even though your principal-and-interest portion stayed the same.

Frequently Asked Questions

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

A 15-year mortgage has a higher monthly payment because you repay the loan in half the time. On a $300,000 loan at 7 percent, the 30-year payment is about $1,995 per month, while the 15-year payment is roughly $2,800 per month. But over the life of the loan, you pay far less total interest with the 15-year option.

Can I pay extra toward principal without changing my monthly payment?

Yes. You can make extra payments toward principal at any time without penalty on most mortgages. This shortens your loan term and reduces the total interest you pay, but your required monthly payment stays the same unless you formally refinance.

Does my credit score affect my monthly payment?

Your credit score does not change the formula for calculating the payment, but it affects the interest rate you are offered. A higher credit score usually means a lower interest rate, which lowers your monthly payment. A lower score means a higher rate and a higher payment on the same loan amount.

What happens if property taxes or insurance spike?

Your lender reviews your escrow account annually. If taxes or insurance have risen, your monthly payment increases to cover the new costs. If the increase is large, your lender may spread it over several months rather than raising your payment all at once.

How do I know if my payment estimate is accurate?

Get a written loan estimate from a lender. By law, they must provide one within three business days of your application. It shows your estimated principal, interest, taxes, insurance, and PMI — the actual numbers the lender will use, not a calculator's rough guess.