The basic formula: principal, interest, taxes, and insurance

Your monthly mortgage payment has four parts, and lenders call the sum of all four your PITI. The first two—principal and interest—go to the lender. The second two—property taxes and homeowners insurance—go to your local government and insurance company, but your lender often collects them and pays them on your behalf.

The principal and interest portion stays the same every month on a fixed-rate mortgage. Property taxes and insurance can change year to year, which means your total payment can shift even though you owe the lender the same amount. If you have an adjustable-rate mortgage, the interest portion itself will change when the rate adjusts, usually after an initial fixed period of three, five, seven, or ten years.

To find your payment, you need four numbers: the loan amount, the interest rate, the loan term in years, and estimates for annual property taxes and homeowners insurance in your area.

Key Takeaways

  • Your monthly payment includes principal, interest, property taxes, and homeowners insurance—often abbreviated as PITI.
  • Principal and interest stay the same on a fixed-rate mortgage, but taxes and insurance can change annually.
  • Online mortgage calculators let you enter your loan amount, rate, and term to see the principal and interest portion instantly.
  • Property tax rates vary widely by county and state, so you need a local estimate rather than a national average.
  • If you put down less than 20 percent, your payment will also include mortgage insurance (PMI), which protects the lender but adds to your cost.

Using an online calculator for principal and interest

The easiest way to see what you will owe is to use a mortgage calculator. You enter the loan amount (the price minus your down payment), the interest rate your lender quoted, and the loan term—usually 15 or 30 years. The calculator does the math and shows you the monthly principal and interest payment in seconds.

Most calculators also let you add property taxes and insurance estimates, which gives you a complete monthly payment figure. If you do not know your local property tax rate, search "[your county] property tax rate" or call your county assessor's office. For insurance, get quotes from at least two insurers—rates vary significantly by company and by what coverage you choose.

Keep in mind that a calculator shows you what the payment would be based on the numbers you enter. The actual payment depends on what rate the lender approves you for, which depends on your credit score, down payment, debt-to-income ratio, and the property itself. A calculator is a planning tool, not a may provide.

How interest rates change your payment

The interest rate is the single biggest lever on your monthly cost. A difference of even half a percentage point can mean hundreds of dollars per month on a $300,000 loan. On a 30-year mortgage at 6 percent, your principal and interest payment is roughly $1,800 per month. At 6.5 percent, it jumps to roughly $1,896. At 5.5 percent, it drops to roughly $1,703.

Your rate depends partly on market conditions—rates move daily based on what the Federal Reserve does and what investors demand. It also depends on your personal finances. A borrower with a 750 credit score and 20 percent down will get a lower rate than one with a 650 score and 5 percent down, even if they apply on the same day.

When you get a rate quote from a lender, ask whether it is a rate lock—a promise that the rate will not change if you close within a certain number of days, usually 30 to 60. Without a lock, the rate can move between now and closing, which changes your payment.

Adding property taxes to your estimate

Property taxes are set by your county or municipality and are based on the assessed value of your home. The tax rate varies dramatically by location. Some counties charge less than 0.5 percent of home value per year; others charge 2 percent or more. A $400,000 home in a low-tax area might have annual taxes of $2,000, while the same home in a high-tax area could owe $8,000 or more.

To find your local rate, search your county assessor's website or call their office directly. They can tell you the effective tax rate for your area and sometimes can estimate what taxes would be on a specific property. Divide the annual amount by 12 to get your monthly portion. Your lender will collect this from you each month and pay it when it is due.

Property taxes can increase over time, especially if your home is reassessed after you buy it or if your local government raises rates. Budget for the possibility that your payment will go up a few years after you close.

Including homeowners insurance in your payment

Homeowners insurance protects your home and belongings against fire, theft, weather, and liability if someone is injured on your property. Your lender requires it as a condition of the loan and will not close without proof of coverage. Like property taxes, the lender collects your insurance premium each month and pays the insurer on your behalf.

Insurance costs depend on the home's age, construction, location, and the coverage limits you choose. A newer home in a low-crime area with a new roof will cost less to insure than an older home in a high-risk flood zone. Get quotes from at least two insurers—rates vary widely, and some companies offer discounts for bundling with auto insurance or for safety features like alarms.

Insurance premiums can increase when you renew your policy, especially if you file a claim or if your insurer raises rates across your area. Plan for your payment to shift when your policy renews each year.

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

If your down payment is less than 20 percent of the home's purchase price, your lender will require private mortgage insurance, or PMI. This is insurance that protects the lender if you stop paying, not insurance that protects you. It adds to your monthly payment but does not build equity or give you any benefit.

PMI typically costs between 0.5 and 1.5 percent of the loan amount per year, depending on your down payment size and credit score. On a $300,000 loan with 10 percent down, PMI might add $150 to $300 per month. You can remove PMI once you have paid down the loan to 80 percent of the home's original purchase price, though you usually have to request it—the lender will not drop it automatically.

If you are considering a down payment below 20 percent, factor PMI into your total payment estimate. It is a real cost that makes the monthly payment higher than the principal and interest alone.

What changes after you close

Your principal and interest payment never changes on a fixed-rate mortgage—you will pay the same amount for 15 or 30 years. But property taxes and insurance will almost certainly change. Property taxes typically increase 2 to 5 percent per year in many areas, though the rate varies by location and by how often your home is reassessed. Insurance premiums can jump when you renew your policy or if you file a claim.

Some lenders also require an escrow account, which means they collect a little extra each month and hold it to cover taxes and insurance when they come due. If they overestimate, you get a refund; if they underestimate, your payment goes up the next year. Ask your lender how they handle escrow adjustments so you are not surprised.

If you have an adjustable-rate mortgage, your interest rate will change on the adjustment date, which means your principal and interest payment will change too. Read your loan documents to understand when the rate adjusts, what it adjusts to, and whether there are caps on how much it can move.

Frequently Asked Questions

Can I use a calculator to see what different down payments would cost?

Yes. Most calculators let you change the down payment amount and see how it affects your monthly payment. A larger down payment lowers the loan amount, which lowers your payment and also eliminates PMI if you reach 20 percent down. You can compare scenarios to see what makes sense for your situation.

What if I want to pay off my mortgage faster than 30 years?

You can choose a 15-year mortgage instead, which has a higher monthly payment but costs far less in interest over the life of the loan. A calculator will show you the payment for both terms so you can decide what fits your budget. Some people also make extra payments toward principal on a 30-year loan to pay it off faster.

Does my credit score affect what payment a calculator shows?

No. A calculator only uses the interest rate you enter. Your actual rate depends on your credit score, so two people with different scores would see different rates from a lender even if they borrow the same amount. Get rate quotes from lenders to see what rate you would actually may have access to for.

Will my payment stay the same if I refinance?

No. Refinancing means taking out a new loan to pay off the old one, so you get a new interest rate, a new term, and a new payment. You might refinance to lower your rate and payment, or to shorten the loan term. The new payment depends on the new rate and term you choose.

What if property taxes or insurance go up after I close?

Your lender will adjust your monthly payment to cover the increase. If taxes or insurance rise, your PITI payment goes up even though your principal and interest stays the same. This is why it is important to budget for the possibility that your payment will increase over time.