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

A house payment has four parts, and lenders add them together to give you one monthly number. The first part is principal and interest — the money that actually pays down your loan. The second is property taxes, which your city or county charges yearly. The third is homeowners insurance, which protects the house if it burns or floods. The fourth is mortgage insurance (if you put down less than 20 percent), which protects the lender if you stop paying.

Most lenders bundle taxes and insurance into your payment and hold that money in an account called an escrow. When your property tax bill comes due, the lender pays it from that account. When your insurance premium renews, the lender pays that too. You never write those checks yourself — they come out of your monthly payment.

The piece most people think of as "the house payment" is actually just the principal and interest. That is the only part that shrinks your loan balance. The other three parts are costs that have to be paid whether you calculate them yourself or let the lender do it.

Key Takeaways

  • Your monthly payment combines four separate costs: principal and interest on the loan, property taxes, homeowners insurance, and mortgage insurance (if your down payment was less than 20 percent).
  • Principal and interest is calculated using the loan amount, the interest rate, and the number of years you have to repay — usually 15 or 30 years.
  • Property taxes and insurance amounts vary by location and the value of your home, so you cannot calculate your full payment without knowing those local costs.
  • Lenders hold your tax and insurance money in escrow and pay those bills on your behalf, so you send one check each month instead of managing multiple bills.

How to calculate principal and interest

The principal and interest portion uses three numbers: how much you borrowed, what interest rate the lender is charging you, and how many months you have to repay it. A $300,000 loan at 6.5 percent interest over 30 years (360 months) produces a different monthly payment than the same loan over 15 years (180 months).

The math itself is complex — it uses something called an amortization formula — but you do not have to do it by hand. Every mortgage lender has a calculator on their website. You enter the loan amount, the interest rate, and the loan term, and it shows you the monthly principal and interest payment when ready. Many banks and credit unions also publish calculators that are free to use without creating an account.

The key thing to understand is that early in the loan, most of your payment goes toward interest. Late in the loan, most goes toward principal. In the first month of a 30-year loan, you might pay $1,625 in interest and only $375 in principal. By month 300, you might pay $50 in interest and $1,950 in principal. The total payment stays the same, but the split changes.

Adding property taxes to the calculation

Property taxes are a yearly cost set by your local government, usually expressed as a percentage of your home's assessed value. A house worth $400,000 in a county with a 1 percent tax rate costs $4,000 per year in property taxes, or about $333 per month. A house worth the same amount in a county with a 0.5 percent rate costs $2,000 per year, or about $167 per month.

Tax rates vary dramatically by state and county. Some areas charge less than 0.5 percent of home value yearly. Others charge more than 2 percent. You can find your local rate by searching "[your county name] property tax rate" or by calling your county assessor's office — they are listed in the county government section of your phone book or online.

When you get a mortgage offer, the lender will estimate your property taxes based on the home's purchase price and your county's rate. That estimate goes into your escrow calculation. If your actual taxes turn out to be higher or lower, your monthly payment adjusts the following year.

Including homeowners insurance in your payment

Homeowners insurance protects the building itself — the structure, the roof, the walls — if it is damaged by fire, wind, theft, or other covered events. It does not cover the land. The cost depends on the home's replacement value (what it would cost to rebuild), your location (hurricane zones and high-crime areas cost more), and the deductible you choose (a higher deductible means a lower premium).

Insurance companies charge yearly premiums that typically range from $800 to $2,000 per year for an average home, though this varies widely. You can get quotes from several insurers before you buy — in fact, lenders often require you to have a quote in hand before they will approve your loan. Once you have a quote, divide the yearly premium by 12 to get the monthly amount that will go into your escrow account.

Your insurance premium can increase each year, especially after a claim or if your area experiences major storms. When it does, your monthly payment increases to cover the new premium.

Understanding mortgage insurance when you put down less than 20 percent

If you borrow more than 80 percent of the home's value — meaning you put down less than 20 percent — the lender requires you to pay mortgage insurance. This protects the lender, not you. It covers the lender's loss if you stop paying and the home sells for less than what you owe.

Mortgage insurance costs vary based on how much you borrowed relative to the home's value and your credit score. A borrower putting down 10 percent might pay 0.5 to 1 percent of the loan amount yearly in mortgage insurance. A borrower putting down 3 percent might pay 1.5 to 3 percent yearly. On a $300,000 loan, that could be $150 to $300 per month.

Mortgage insurance is not permanent. Once you have paid your loan down to 80 percent of the home's original value, you can request that the lender remove it. Some loans remove it automatically at that point; others require you to ask. Check your loan documents or call your lender to find out the rule for your specific mortgage.

Putting the four pieces together

Here is a concrete example. Say you are buying a $350,000 home, putting down $70,000 (20 percent), and borrowing $280,000 at 6.5 percent interest over 30 years. Your county's property tax rate is 1.2 percent yearly. Your homeowners insurance quote is $1,200 per year. Because you are putting down exactly 20 percent, you do not owe mortgage insurance.

Principal and interest: $1,773 per month (from a lender's calculator). Property taxes: $350,000 × 1.2 percent = $4,200 yearly, or $350 per month. Homeowners insurance: $1,200 yearly, or $100 per month. Total monthly payment: $1,773 + $350 + $100 = $2,223.

If that same buyer had put down only $35,000 (10 percent) instead, they would borrow $315,000, owe mortgage insurance of roughly $300 per month, and have a total payment of around $2,500 or more. The difference in down payment size directly changes the monthly cost.

Tools that do the calculation for you

You do not need to do any of this math yourself. Most mortgage lenders provide a calculator on their website where you enter the loan amount, interest rate, loan term, property tax rate, insurance estimate, and down payment percentage. The calculator shows you the total monthly payment when ready.

Some calculators also let you adjust numbers to see how different choices affect your payment. You can see what happens if you choose a 15-year loan instead of 30 years, or if you put down 15 percent instead of 10 percent. This helps you understand which decisions have the biggest impact on what you will owe each month.

If you are shopping for a mortgage, ask each lender for a Loan Estimate — a standardized form that shows your projected principal and interest payment, property taxes, insurance, mortgage insurance (if applicable), and the total monthly payment. This form is required by federal law and makes it straightforward to compare offers from different lenders side by side.

Frequently Asked Questions

Does my house payment change every month?

The principal and interest portion stays the same for the life of the loan (on a fixed-rate mortgage). But property taxes and insurance can increase, which raises your total payment. If your escrow account runs short because taxes or insurance cost more than estimated, your monthly payment increases to cover the difference.

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

A 15-year mortgage has a higher monthly payment but you pay far less interest overall because you are repaying the loan in half the time. A 30-year mortgage has a lower monthly payment but costs more in total interest. The choice depends on whether you prioritize lower monthly costs or paying off the loan faster.

Can I pay just principal and interest without taxes and insurance?

No. Property taxes and insurance are legal requirements — the government requires you to pay taxes on the property, and the lender requires you to carry insurance to protect their investment. These costs are bundled into your payment through escrow.

What happens if my property taxes go up?

Your lender reviews your escrow account once a year. If taxes or insurance have increased, they raise your monthly payment to cover the new costs. You will receive notice of the change before it takes effect.

How do I know what interest rate I will get?

Interest rates depend on market conditions, your credit score, your down payment size, and the loan term. Lenders publish their current rates, and you can get quotes from multiple lenders to compare. Rates change daily, so shop around before you commit.