How to Measure Your Home for New Windows

Before you can purchase new windows for your home, taking measurements can help you find and price a product of the proper dimensions. Measuring windows for replacement is not as simple or straightforward as it sounds, so if you’ve never done it before, getting proper guidance is important. Below, we’ve listed the steps to measure your home for new windows.

When taking measurements, don’t forget to write all measurements down in one location, and label each specific window to be sure that you know which measurements correspond to which windows in your home. You can label your windows by numbering them, or by assigning names that designate the location of the window (example: “living room northeast corner”). Finally, remember to measure twice to ensure that the numbers you record will match the true dimensions of your windows.

Learn the Parts of the Window

Every window is made up of parts, and each part has its own name. Before you can measure your home’s windows, it’s helpful to learn the parts of your home’s windows.

  1. Sash is the part of the window that moves up and down (on double-hung windows).

  2. Jamb is the stationary part of the window that the sash moves against when it slides up and down.

  3. Sill is the horizontal board that meets the bottom sash when it’s closed.

Measure to Check for Square

Ideally, each corner of your existing window frames will have a 90° measurement. To determine whether your windows are properly square, stretch the tape measure from the inside upper right corner of the jamb to the inside lower-left corner of the jamb. Next, measure the inside upper left corner of the jamb to the inside lower right corner of the jamb. You’ll be able to tell if the window is square if the two measurements are within 1/4 of an inch of each other.

If the difference between the measurements is greater than 1/4 of an inch, this is an indication that the window is not square. Talk to your window installer about this problem.

Measure Window Height

To determine window height, measure the space inside the window starting at the top jamb down to the sill. Take three measurements: one on the far left, one on the far right, and one in the middle.

Important note: the sill is the board that the window rests on when it’s closed. To access the sill, you’ll have to open the window.

Circle the measurement that is the shortest of the three.

Measure Window Width

Measure the width of the window by positioning the tape measure against the jamb on each side of the window. Measure the width of the window at three points, including the lowest part of the window, the top part of the window, and the section in the middle.

To measure the window width, you’ll have to move the sash so it doesn’t get in the way. Open the window when measuring the bottom of the jamb, lower the upper sash so it doesn’t get in the way when you’re measuring the top. To measure the jamb in the middle, open the window and measure the point that is as close to the middle as you can get.

Circle the measurement that is the shortest of the three.

Measure Window Depth

Traditional houses are naturally deep enough for replacement windows. You’ll only need to measure window depth if you live in a mobile home or in a prefabricated or modular home. Talk to your window contractor if you have concerns about window depth.

Open the window and measure the sill from the trim in back to the trim in front. The measurement must be at least 3 1/4 of an inch to fit. If the measurement is not thick enough, talk to your window installation contractor about your options.

Round Circled Measurements Down

Round the measurements down to the nearest 1/8 of an inch, unless the measurement is already at a 1/8 inch increment. For example, if the measurement you took was 28 3/16 inches, round to 28 1/8 inches.

Contact Your Window Installer

Once you’ve taken the time to measure for new windows, contact your window installer to get a quote and start the window purchase and installation process. At FAS Windows and Doors, we help homeowners like you install quality windows that can improve your home’s value while increasing energy efficiency. Having the measurements can speed along the process and help you get a quick idea of the cost of your window replacement project. To find out more about window installation for your home’s windows, contact us today.