Your mortgage payment depends on the loan amount, interest rate, and how many years you borrow for

Your monthly mortgage payment is built from three numbers: how much you borrow, what interest rate the lender charges, and the length of the loan (usually 15 or 30 years). A $300,000 loan at 6.5% over 30 years costs roughly $1,896 per month in principal and interest alone. The same loan at 7.5% costs roughly $2,098. A 15-year loan at 6.5% costs roughly $2,896. Small shifts in rate or term create large shifts in what you pay each month.

Your actual bill will be higher than the principal-and-interest number because it includes property taxes, homeowners insurance, and possibly mortgage insurance. These costs vary by location and your down payment size, so there is no single answer—but you can calculate the pieces separately and add them together.

Key Takeaways

  • Principal and interest make up the core payment, and you can calculate this yourself using an online mortgage calculator or a spreadsheet formula if you know the loan amount, interest rate, and loan term.
  • Property taxes and homeowners insurance are added to your principal-and-interest payment, and both vary by location and home value.
  • If you put down less than 20 percent, you will also pay mortgage insurance (PMI), which protects the lender if you default.
  • Your lender will provide a Loan Estimate within three days of your application, which shows all four components of your monthly payment.

How to calculate principal and interest yourself

The formula for a fixed-rate mortgage payment is: M = P [ r(1 + r)^n ] / [ (1 + r)^n – 1 ], where M is your monthly payment, P is the loan amount, r is the monthly interest rate (annual rate divided by 12), and n is the total number of payments (years times 12).

You do not need to do this by hand. Free online mortgage calculators (available from Bankrate, NerdWallet, and most major lenders) ask you to enter the loan amount, interest rate, and loan term, then show you the monthly payment instantly. A spreadsheet like Excel or Google Sheets also has a built-in PMT function that does the same calculation. Enter the monthly rate, number of payments, and loan amount, and it returns your payment.

The result is principal and interest only. This is the amount that goes toward paying down the loan and the lender's interest. It does not include taxes, insurance, or mortgage insurance.

Property taxes and homeowners insurance

Property taxes are set by your county or municipality and are based on the assessed value of your home. They vary widely by location—some areas charge less than 0.5 percent of home value per year, while others charge over 2 percent. Your real estate agent or the county assessor's office can tell you the rate for the specific property you are buying.

Homeowners insurance protects your home against fire, theft, and weather damage. Lenders require it as a condition of the loan. Annual premiums vary based on the home's age, location, construction type, and your coverage limits. Getting quotes from three insurers (State Farm, Allstate, GEICO, and local companies all offer homeowners policies) gives you a realistic range. Divide the annual premium by 12 to get the monthly cost.

Both property taxes and insurance are usually paid through escrow—your lender collects a portion each month along with your principal and interest, holds the money, and pays the bills on your behalf when they come due. This is why your monthly payment statement shows four separate line items.

Mortgage insurance if you put down less than 20 percent

If your down payment is less than 20 percent of the home price, lenders require private mortgage insurance (PMI). This protects the lender, not you, if you stop paying. PMI typically costs 0.5 to 1.5 percent of the loan amount per year, though the exact rate depends on your credit score, the size of your down payment, and the lender.

A $300,000 loan with PMI at 1 percent costs $3,000 per year, or $250 per month. Once you build 20 percent equity in the home (either through payments or home appreciation), you can request that PMI be removed. Some loans remove it automatically once you reach that threshold.

If you are putting down less than 20 percent, ask the lender to show you the PMI cost in writing before you commit. It is a real monthly expense that affects affordability.

Using the Loan Estimate to see your full payment

Within three business days of submitting a mortgage application, your lender must send you a Loan Estimate—a standardized form that shows your estimated monthly payment broken into all four parts: principal and interest, property taxes, homeowners insurance, and mortgage insurance (if applicable). The form also lists all fees you will pay at closing.

The Loan Estimate is not a final bill—interest rates can change, property taxes may be reassessed, and insurance quotes can shift. But it gives you a realistic picture of what your payment will be. Compare Loan Estimates from multiple lenders side by side; the form is designed to make this easy because every lender uses the same layout.

Keep the Loan Estimate until closing. You will receive a final Closing Disclosure one business day before you sign the deed, and you can check it against the Loan Estimate to catch any surprises.

What changes your payment after you lock in the rate

Once you lock your interest rate with the lender, your principal-and-interest payment is fixed for the life of the loan (assuming a fixed-rate mortgage). Property taxes and insurance can change year to year, so your escrow payment may go up or down. If your home is reassessed for taxes or your insurance premium increases, your lender will adjust your monthly payment to cover the new costs.

If you refinance—taking out a new loan to pay off the old one—you get a new interest rate and a new payment. Refinancing makes sense if rates drop significantly or if you want to shorten the loan term, but it comes with closing costs and a new application process.

Frequently Asked Questions

Can I pay off my mortgage early without a penalty?

Most fixed-rate mortgages have no prepayment penalty, meaning you can pay extra toward principal whenever you want. Check your loan documents or ask your lender to confirm. Some adjustable-rate mortgages (ARMs) do have penalties, so verify before signing.

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

A 15-year mortgage has higher monthly payments but you pay far less interest over the life of the loan. A 30-year mortgage has lower monthly payments but costs more in total interest. Choose based on what monthly payment fits your budget and how long you plan to stay in the home.

Does my credit score affect my mortgage payment?

Your credit score does not change the payment formula, but it affects the interest rate the lender offers you. A higher score usually gets you a lower rate, which lowers your monthly payment. A lower score gets you a higher rate. The difference can be 0.5 to 1.5 percent, which translates to hundreds of dollars per month.

What if interest rates drop after I lock my rate?

You are locked in at your rate and cannot benefit from the drop unless you refinance. Refinancing means applying for a new loan, paying closing costs again, and restarting the loan term. It only makes financial sense if the new rate is low enough to offset those costs within your timeline.

How much should I budget for property taxes and insurance?

Ask your real estate agent or the county assessor for the property tax rate, then multiply it by the home's assessed value. For insurance, get quotes from at least three companies. Add both to your principal-and-interest payment to see your full monthly cost before you commit to the purchase.