Whether your existing windows are old, outdated, or dilapidated, you might be thinking about or planning on replacing them. That’s a wise investment, as new windows will not only enhance the aesthetic appeal of the interior and exterior of your home. In fact, new windows will also help to improve the energy efficiency of your house, save you money on your utility bills, and improve your comfort, to boot. Whatever the reason, if you’re replacing your windows, knowing how to measure each window you want to replace is an absolute must – unless you hire professionals to do it.

How to Measure for Replacement Windows

Proper measurements will ensure that the window installation process goes off without a hitch. They’ll fit correctly, they’ll look great, and most importantly, they’ll function properly. As the saying goes, “measure twice, cut once”. But how do you measure for replacement windows? Follow the simple step-by-step instructions below.

Check for Squares

First things first, you need to check to make sure your windows are square. In other words, each corner measures 90 degrees. While standard window sizes do vary, checking to make sure that your replacement windows will require a 90-degree angle is super important. Here’s how to check your windows for squares (note, the measurements have to be taken from inside your house):

  • Place a tape measure in the top right corner of the window, right where the horizontal and vertical trim boards come together.
  • Draw the measuring tape out diagonally down to the bottom left corner of the window, again, where the horizontal and vertical trim boards come together.
  • Check the measurement and jot it down.
  • Repeat the process again, from the top left corner to the bottom right corner of the window.
  • Check the second measurement and jot it down.

Once you’ve taken two measurements, compare them. If they’re within ¼ of an inch of one another, you’ll be able to fit a standard replacement window into the opening. If the two measurements don’t match up and are more than 1/4 of an inch – here’s the important part – the window isn’t square.

As a result, you won’t be able to use a standard window replacement. Instead, you’ll need to use an alternative replacement window. If that’s the case, you can replace the frame or opt for a newly constructed window.

Measure the Width

In order to achieve a perfect fit with a standard window, you need to know the width and height of the window. These measurements have to be taken at three spots: the top, the middle, and the bottom of the current window. You’ll have to take all three measurements on each side of the interior of the window jambs (jamb to jam); the main vertical section that creates the window frame’s exterior.

Here’s how to check the width of your window:

  • Measure the distance between the top of the window between the two jambs. Make sure the window is closed.
  • For the middle measurement, measure between the two jambs as close to the middle of the window as possible. Make sure the window is opened.
  • With the window open, measure the bottom between the two jambs.

Record the measurements – all three. The smallest of the three is the width of the window, so make sure to highlight that number.

Measure the Height

You’ll also need to take three measurements to determine the height of the window: the right, middle, and left. Starting at the right side, measure the header (head jamb), which is the upper board that sits horizontally above the window, down to the bottom window sill (where the window sash rests when the window is closed). Repeat the process in the center and on the left side of the window.

Jot down all three measurements. The shortest measurement of the three is the height of the window, so be sure to notate this number.

Finalize the Measurements – Double-Check

After you’ve taken all of your measurements, you can determine the size you’ll need for your replacement window. Take the measurements you highlighted for the width and height, and round down to the nearest 1/8 inch. If the original measurements fall within 1/8-inch increments, no adjustments will be necessary. You can use those measurements to order your replacement window.

How to Measure Windows for Replacement

Measuring for replacement windows is a relatively simple and straightforward task. If, however, your windows aren’t square or you aren’t confident with your ability to take accurate measurements, it’s best to err on the side of caution and hire a local window replacement professional to take the measurements for you, instead.

Discount Window and Door of Omaha

At Discount Window and Door of Omaha, we are committed to providing the best quality doors and replacement windows. We employ the most skilled installers to ensure the highest standard of quality service. Our Omaha door and window installers are highly trained, certified industry professionals with years of experience, including some second and third-generation employees.

Contact us for a FREE Estimate!
(402) 884-8989