How Do I Measure Windows?

By Alex Hawkins Updated February 5, 2024

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Taking window measurements is the most important step in a window replacement project. Having accurate measurements is essential for a proper installation without energy leaks or safety risks. It can also save you from costly mistakes when ordering new ones.

In this guide, we’ll break down the three main steps to window replacement and recommend the best window brands on the market.





Terms to Know

Before measuring your windows, learn these terms to ensure you’re measuring the correct parts:



How to Measure Home Windows

Below are three simple steps you can take to measure your windows correctly. 

Step 1: Measure the Width

Using your measuring tape, measure the distance between the jambs at the top, middle, and bottom of the window. Make sure to measure from the surface of the jambs and not from the outer moldings, such as trim strips or parting beads. Use the smallest of the three width measurements to order your window.

Step 2: Measure the Height

Using the surface closest to the inside of the window, measure from the high point of your window sill to the top of the window opening. Measure from the left side, the center, and the right side of the window. Again, use the smallest of these three height measurements to order the window.

Step 3: Measure Depth

Measure the window edge-to-edge from the outside of the frame to the inside. Do this in several locations around the window frame and use the smallest measurement. It should be a minimum of three-and-one-fourth inches to properly fit a replacement window. Otherwise, you may need additional materials to fill the gap. This is typically the most accurate measurement of depth.

Another option is to measure the depth on each side of the glass and add the two numbers together. An installer will remove any pulleys or parting strips (or the vertical strips between the window sashes), so ignore those while measuring.



How to Find a Local Window Installer

Once you know which type of new window you want, you’ll most likely want to hire a professional window installer. Here are some steps you can take to find a reputable installer.



Our Recommendation

Measuring your windows is a necessary step for window installation. However, you may be able to avoid this task by hiring a replacement window company. A professional window installer guarantees your windows are installed correctly and backed by robust warranties. Below are some of our top-recommended companies for professional window installation


Best for Sunrooms: Champion Windows

Fast Facts:

*Available in Alabama, Colorado, Georgia, Idaho, Indiana, Iowa, Kansas, Kentucky, Massachusetts, Michigan, New Mexico, North Carolina, Ohio, Tennessee, Texas, South Carolina, and Wisconsin.

What we like: Champion started as a small, regional window manufacturer in 1953 in Cincinnati. It initially produced affordable aluminum storm windows, storm doors, awnings, and screen rooms.

Now, it has a wide selection of window lines—all with its Energy Star-certified Comfort 365 Window Glass. This glass has a specialized low-emissivity (Low-E) coating and an insulating argon gas filling that blocks roughly 94% of harmful ultraviolet (UV) rays. These features ensure your home stays cool during summer and warm in winter while still receiving plenty of natural sunlight. 

Champion is one of the best window brands for a sunroom or patio project, as it offers completely customized sunrooms with an in-depth, personalized installation process.

Learn more: Champion Windows Review



Best Warranty: Castle Windows

Fast Facts:

*Available in Connecticut, Indiana, Maryland, Michigan, New Jersey, New York, Ohio, Pennsylvania, Rhode Island, Virginia, and West Virginia.

What we like: Castle Windows has been providing window replacement services since 1977. Notably, it offers design-friendly double-hung windows and basement hopper windows with double weather-stripping, insulated glass, and a maintenance-free vinyl frame.

For added convenience, Castle has a 24/7 customer support line and a transferable lifetime warranty covering all parts, glass, and window components, including screens. The warranty also covers workmanship with free labor on all services.



Best Selection: Renewal by Andersen

Fast Facts:

What we like: Andersen is one of the largest and most respected window manufacturers in the United States. In addition to featuring one of the highest-rated customer service teams, Andersen offers 35 different window types. Each Andersen window has multiple operational styles, color options, frame types, and shapes.

Renewal by Andersen is the company’s white-glove installation service. It handles all aspects of the installation process, from measuring to inspection. We recommend Renewal by Andersen if you want a completely hands-free home improvement project.

Learn more: Renewal by Andersen Review



How To Measure Windows FAQ

Do you measure height or width first in windows?

It doesn’t matter whether you measure your window height or width first, but you should always list window measurements with width before height. 

How do you read window sizes?

When you see a window size, the first number refers to the width and the second number refers to height. 

Are replacement windows smaller than original windows?

Yes, replacement windows are often smaller than the original windows installed. This is because the opening in your wall has to be slightly smaller than the window itself to ensure a tight fit.



How We Chose the Top Window Brands

We researched and analyzed dozens of window manufacturers. We then crafted a rating system based on each brand’s standard and energy-efficient product offerings.

We spoke directly to representatives at each company to learn how the installation process works and determine how each brand personalizes its windows for each home. We also closely analyzed each company’s warranty options to ensure their product and labor guarantees match or exceed industry standards. 

Finally, we assessed the manufacturer’s years of experience and customer reputation. In addition, we analyzed the 100 most recent Google Reviews for each provider across various locations and branches.