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

Your monthly payment is determined by three numbers: how much you borrowed, the interest rate your lender charges, and the length of the loan (called the term). A larger loan amount or higher interest rate raises your payment. A longer term spreads the cost over more months, which lowers each payment but means you pay more interest overall. Most home loans are 15-year or 30-year mortgages, though other terms exist.

Your payment also includes more than just principal and interest. Most lenders require you to pay property taxes and homeowners insurance as part of your monthly bill. If you put down less than 20 percent, you will also pay mortgage insurance (PMI). These costs vary by location and your specific situation, so the total payment is usually higher than a straightforward interest calculation would show.

Key Takeaways

  • A mortgage payment calculator takes your loan amount, interest rate, and loan term and shows you the principal and interest portion in seconds.
  • Your actual monthly payment includes property taxes, homeowners insurance, and possibly mortgage insurance — not just principal and interest.
  • A 30-year mortgage has a lower monthly payment than a 15-year mortgage on the same loan, but you pay significantly more interest over the life of the loan.
  • Your interest rate is the single biggest factor you can influence before closing — even a difference of 0.5 percent changes your payment by over $100 per month on a $300,000 loan.

How to use a mortgage payment calculator

A mortgage calculator is the fastest way to see what your payment will be. You enter three pieces of information: the loan amount (the price minus your down payment), the interest rate, and the loan term in years. The calculator then shows you the monthly principal and interest payment.

Most lenders' websites have a calculator you can use for free. Bankrate, NerdWallet, and the Consumer Financial Protection Bureau (CFPB) all offer calculators that do not require you to enter your name or contact information. Enter different numbers to see how changes affect your payment — this is how you can compare a 15-year versus 30-year loan, or see what happens if you can negotiate a lower interest rate.

Keep in mind that the calculator shows only principal and interest. Your actual bill from the lender will be higher because it includes taxes, insurance, and possibly PMI. Your lender can give you an estimate of those costs once you have a specific property and loan offer.

What principal and interest actually means

Principal is the amount you borrowed. Interest is what the lender charges you for lending that money. Early in your loan, most of your payment goes toward interest. As time goes on, more of each payment goes toward principal. By the end of the loan, you are paying mostly principal.

For example, on a $300,000 loan at 6.5 percent interest over 30 years, your first payment is about $1,896. Of that, roughly $1,625 goes to interest and only $271 goes to principal. By payment 300 (near the end), that same $1,896 is split almost the opposite way — about $1,800 goes to principal and only $96 to interest. This is why paying extra toward principal early in the loan saves you the most money in interest.

How property taxes and insurance change your total payment

Your lender almost always requires you to pay property taxes and homeowners insurance as part of your monthly mortgage payment. These amounts vary widely depending on where the property is located and what it is worth. Property taxes in some states are under 0.5 percent of the home value per year; in others they exceed 2 percent. Homeowners insurance ranges from about $800 to $2,000 per year depending on the home's value, location, and your coverage choices.

Your lender collects these payments from you each month and holds them in an escrow account, then pays the bills when they are due. This protects the lender because it ensures the taxes and insurance stay current — if they lapsed, the lender's collateral (your home) would be at risk. When you get a loan estimate from a lender, it will show you an estimate of these costs so you can see your true total payment.

Mortgage insurance (PMI) and when it applies

If you put down less than 20 percent of the purchase price, your lender will require you to pay mortgage insurance. This protects the lender if you stop paying the loan. PMI typically costs between 0.3 and 1.5 percent of the loan amount per year, depending on how much you put down and your credit score. On a $300,000 loan with 10 percent down, PMI might add $150 to $300 per month to your payment.

PMI is not permanent. Once you have paid down the loan to 80 percent of the original home value (through a combination of payments and home appreciation), you can request that PMI be removed. Some loans allow you to remove it automatically once you reach that threshold. Ask your lender about their PMI removal policy before you close.

How interest rates affect your payment

Interest rate changes have a large effect on your monthly payment. On a $300,000 loan over 30 years, the difference between 5.5 percent and 6.5 percent is about $170 per month — that is over $61,000 over the life of the loan. The difference between 6.5 percent and 7.5 percent is another $170 per month.

Your interest rate depends on several factors: the current market rate (which changes daily), your credit score, your down payment size, the loan term, and the type of loan (fixed-rate versus adjustable-rate). You can see current rates from multiple lenders and compare them. Even a 0.125 percent difference between lenders is worth shopping for, because it compounds over 30 years.

If you are not ready to buy yet, you can lock in a rate for a limited time (usually 30 to 60 days) while you shop for a home. Once you have an offer accepted, you can lock the rate for the full time until closing, which is typically 30 to 45 days.

15-year versus 30-year mortgages and payment differences

A 15-year mortgage has a higher monthly payment but costs much less in total interest. A 30-year mortgage has a lower monthly payment but you pay interest for twice as long. On a $300,000 loan at 6.5 percent, a 30-year mortgage costs about $1,896 per month, while a 15-year mortgage costs about $2,896 per month — a difference of $1,000. Over the full term, the 30-year loan costs about $382,000 in interest, while the 15-year loan costs about $121,000 in interest.

The right choice depends on your budget and goals. If you can afford the higher payment and want to build equity faster and pay less interest, a 15-year loan makes sense. If you want the lowest possible monthly payment and prefer to invest extra money elsewhere, a 30-year loan is more flexible. Many people choose a 30-year loan but make extra payments when they can, which gives them the flexibility of a longer term with some of the interest savings of a shorter one.

What happens if rates change before you close

Interest rates change daily based on market conditions. If you are in the process of buying a home, your lender will lock your rate for a set period — usually 30, 45, or 60 days. This means your rate will not change during that time, even if market rates go up. If rates go down, you cannot take advantage of the lower rate unless you pay a fee to re-lock at the new rate.

If your closing is delayed and your rate lock expires, your rate will adjust to the current market rate. This is why it is important to understand your rate lock period and plan your closing timeline accordingly. If you are concerned about rates rising, you can pay a fee to extend your lock or to lock in a rate before you have an offer accepted (called a rate lock or rate hold).

Frequently Asked Questions

Can I use a mortgage calculator to see what I can afford?

A calculator shows you what your payment will be for a specific loan amount, but it does not tell you what you can afford. To determine affordability, you also need to consider your income, other debts, savings, and how much you want to spend on housing. Most lenders use a debt-to-income ratio — they want your total monthly debt payments (including the new mortgage) to be no more than 43 to 50 percent of your gross monthly income. A mortgage calculator cannot see your full financial picture.

Why is my actual payment higher than what the calculator showed?

The calculator showed principal and interest only. Your actual payment includes property taxes, homeowners insurance, and possibly PMI. These can add $300 to $800 or more per month depending on your location and down payment. Your lender's loan estimate will show all of these costs together so you can see the true total.

What if I want to pay off my mortgage early?

You can make extra payments toward principal at any time without penalty on most mortgages. Even small extra payments early in the loan save significant interest. Some people make one extra payment per year, while others round up their payment by $100 or $200 per month. Ask your lender whether they charge any fees for early payoff before you commit to a strategy.

Does my credit score affect my monthly payment?

Your credit score does not change the formula for calculating your payment, but it does affect the interest rate you are offered. A higher credit score typically qualifies you for a lower rate, which lowers your payment. The difference between a 620 credit score and a 760 credit score can be 1 to 2 percentage points, which translates to $200 to $400 per month on a $300,000 loan.

Can I change my loan term after I close?

You cannot change the term of your existing loan, but you can refinance into a new loan with a different term. Refinancing means taking out a new loan to pay off the old one. This involves closing costs and a new process, so it only makes sense if the savings are significant. Some people refinance from a 30-year to a 15-year loan when their financial situation improves, or from a 15-year to a 30-year if they need lower payments.