Under "Home price," enter the price (if you're buying) or the current value (if you're refinancing). NerdWallet also has a .

Under "Down payment," enter the amount of your down payment (if you’re buying) or the amount of equity you have (if refinancing). A  is the cash you pay upfront for a home, and  is the value of the home, minus what you owe.

On desktop, under "Interest rate" (to the right), enter the rate. Under "Loan term," click the plus and minus signs to adjust the length of the mortgage in years.

On mobile devices, tap "Refine Results" to find the field to enter the rate and use the plus and minus signs to select the "Loan term."

You may enter your own figures for ,  and , if you don’t wish to use NerdWallet’s estimates. Edit these figures by clicking on the amount currently displayed.

The mortgage calculator lets you click "Compare common loan types" to view a comparison of different loan terms. Click "Amortization" to see how the principal balance, principal paid (equity) and total interest paid change year by year. On mobile devices, scroll down to see "Amortization."

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The mortgage payment calculation looks like this: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1]

The variables are as follows:

Determining what your monthly house payment will be is an important part of figuring out how much house you can afford. That monthly payment is likely to be the biggest part of your cost of living.

Using NerdWallet’s mortgage calculator lets you estimate your mortgage payment when you buy a home or refinance. You can change loan details in the calculator to run scenarios. The calculator can help you decide:

Mortgage lenders are required to assess your ability to repay the amount you want to borrow. A lot of factors go into that assessment, and the main one is debt-to-income ratio.

Your  is the percentage of pretax income that goes toward monthly debt payments, including the mortgage, car payments, student loans, minimum credit card payments and child support. Lenders look most favorably on debt-to-income ratios of 36% or less — or a maximum of $1,800 a month on an income of $5,000 a month before taxes.

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If your mortgage payment included just principal and interest, you could use a bare-bones mortgage calculator. But most mortgage payments include other charges as well. Here are the key components of the monthly mortgage payment:

Typically, when you belong to a homeowners association, the dues are billed directly, and it's not added to the monthly mortgage payment. Because HOA dues can be easy to forget, they're included in NerdWallet's mortgage calculator.

The mortgage calculator lets you test scenarios to see how you can reduce the monthly payments:

Your monthly payment can go up over time if: