How does a home loan mortgage calculator work?

Question: "Are home loan mortgage calculators accurate? What kind of information do I have to gather to be able to use them."

Some calculators are better than other. Generally speaking, the ones you find on popular websites (Bankrate.com, Interest.com, etc.) will be most reliable. The more information you have to put into the mortgage calculator, the better. This will give you a more accurate monthly payment amount.

The exact function will vary from one tool to another. But most home loan mortgage calculators ask for the following items, at a minimum:

  • The mortgage amount (what you're borrowing from the lender)
  • The term / length of the loan (e.g., 30 years)
  • The interest rate on the loan

This is the minimum information needed, in order to give you a monthly payment amount. Based on this information, the home loan mortgage calculator would take the loan amount, plus interest, and break it down into monthly payments for you. This gives you a rough idea of how much you'll be paying each month, based on the amount you're borrowing and the interest rate you're able to secure.

Some home loan calculators ask for more information, though it's usually an optional field. For example, if you can enter an approximate amount for property taxes, you'll get a better picture of the total cost. Taxes and insurance affect the size of your monthly payment too, though not nearly as much as the principal and the interest. So, even if you only have the three items listed earlier in this article (loan amount, term, and interest rate), you'll get a good idea of your monthly payments. Just realize that they'll probably be a bit higher, in reality, once taxes are added on.

Set Your Budget, Before Using Mortgage Calculators


As a home buyer, one of the smartest things you can do is to establish a monthly budget for yourself. You should do this before you start using home loan mortgage calculators, applying for loans, or even talking to lenders. Why? Because it's possible to get approved for a loan that's simply too big for you. It happens all the time.

Remember, you are the only person looking out for your long-term financial security. The lender doesn't care about that, because they'll probably sell your loan into the secondary mortgage market (Freddie Mac, Fannie Mae, Wall Street, etc.). They don't bear the long-term risk that you do. It's a broken system, but that's the way it works. Before you start playing around with home loan mortgage calculators, you should have a good idea what you can afford to spend each month. Don't let the calculator or the lender set your budget for you -- do it yourself, and do it early on in the process.

Related article:
Free mortgage calculators and how to use them
How to calculate your monthly payments

I hope this answers your question, and I wish you well in your home-buying adventure. Good luck in the new year.

Labels: