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How To Measure Windows Step-by-Step (2024 Guide)

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Author Icon By Jessica Wimmer Updated 12/19/2023

Mismeasuring your windows leads to costly mistakes and headaches. This guide pulls from the hundreds of hours we spent researching the best replacement windows on the market to break down how to measure your windows step-by-step. We at the This Old House Reviews Team also provide some of our top recommendations for professional window installers once your measurements are completed.


Windows Glossary

Make sure you have all the proper knowledge when it comes to windows with the following terms:

  • Balance: These are spring-loaded, mechanical devices commonly found in single- and double-hung windows. They help counterbalance the weight of the sash during opening and closing.
  • Frame: The window frame surrounds and supports the entire window system. A window frame consists of the head, jamb, and sill.
  • Head: The window head refers to the central horizontal part that forms the top of the window frame.
  • Jambliner: This is the strip on each side of a window that helps fit the window sash.
  • Jambs: These are the main vertical parts that form the sides of the window frame.
  • Lift: The lift refers to the handle for raising the lower sash.
  • Rails: For double-hung windows, there are three rails. The upper and lower rails create the horizontal piece of the window sash. The middle rail, or the check rail, is where the bottom part of the upper sash meets the upper part of the lower sash.
  • Sill: This term refers to the central horizontal part that forms the bottom of the window frame.
  • Sash: This is the movable part of a window that holds the glass.
New Windows in Home
Window Replacement

Window replacement typically costs $300–$2,100 per window, depending on the window type.

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Window Repair

Window repair typically costs $100–$600, but it can vary based on the type of repair.

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Window Cleaning Cost

Window cleaning typically costs $150–$300 for an entire home.

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How To Measure Windows

Once you have your tape measure ready, use these three primary steps to accurately measure your existing windows:

  1. Width: First, measure the window’s width. To do so, measure between the jambs at the window opening’s top, middle, and bottom. Measure from the surface of the jambs and not from the trim strips or parting beads. When you order a new window, use the smallest of these three width measurements for the dimensions.
  2. Height: Next, you want to measure the window’s height. Measure from the high point of the window sill at the surface closest to the inside of the window to the top of the window opening. Take this measurement from the left side, center, and right side of the window. Again, use the smallest of these three height measurements when you order the new window.
  3. Depth: Finally, you’ll need to measure the depth of the window opening. There must be at least 3 1/4 inches of opening depth between the inside window trim and the outside blind stop strip. This much area is necessary to accept the depth of the replacement window. If your window features any pulleys or parting strips, you should ignore them when measuring depth dimensions, as the installer will remove them during installation.

Finding a Local Window Installer

Once you have the measurements and know what type of window you want, you may want to find a window installer rather than conduct the window replacement installation yourself. Many companies offer window installation. One way to whittle down your options is to look for certified installers for the particular window brand you want. You should also confirm which companies service your address.

Use our tool below to quickly connect with reputable, certified window installers that service your ZIP code and schedule in-home assessments.

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You can also check out some of our top recommendations for professional window replacement below. 

Champion Windows: Best Financing and Discounts

  • Our rating: 88.5 out of 100
  • Warranty: Limited lifetime warranty
  • Price range: $350–$800

Champion Windows started in 1953 and now provides multiple window lines in 17 states. The company’s ColorBond aluminum window line uses nontoxic heat-reflective materials to maintain cool temperatures in your home. The TimberBond line offers custom wood grain finishes, including cherrywood, dark oak, and English oak.

In addition, Champion Windows provides complete sunroom and patio services. The company builds all-season and three-season sunrooms with custom-shaped windows tailored to your home’s style.

Castle Windows: Best Warranty

  • Our rating: 88 out of 100
  • Warranty: Transferable lifetime warranty
  • Price range: $300–$600

Castle Windows has offered high-quality replacement windows, doors, roofing, and siding services since 1977. The company provides accessible windows with double weather stripping for durability. Castle creates made-to-order windows rather than offering specific lines. It has wood, fiberglass, and aluminum window options. 

The company includes a transferable lifetime warranty covering all window parts, including glass, screens, and other components. The warranty also covers workmanship with free labor on all services—a standout compared to the standard manufacturer warranties other window replacement companies offer.

Renewal by Andersen: Most Hands-Free Experience

  • Our rating: 94 out of 100
  • Warranty: Limited and limited lifetime warranties 
  • Price range: $500–$3,000

Andersen is one of the most recognizable names in the windows industry. Its subsidiary, Renewal by Andersen, offers customized replacement windows with white-glove service. In addition, you can schedule a free consultation with a windows specialist to determine your window needs and specifications. 

Renewal has 35 different window styles, including specialty shapes. In addition, you can select from various exterior colors, interior colors, glass types, hardware colors, grille patterns, and an optional Truscreen insect screen. Those who want more standard Andersen windows can find the brand at popular retailers such as Home Depot. 

Andersen backs its products with a limited or limited lifetime warranty, depending on the product.


Our Conclusion

Measuring windows is a key step in replacing your windows. Grab your tape measure and ensure you take the measurements in the right spots. While a few windows might be a DIY job, you can check out professional window installers to make sure the job goes right for one window or the whole house.

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FAQ About How To Measure Windows

How do you read window sizes?

When you look at window sizes, you will see a four-digit figure. The first two numbers are the width of the window, and the second two numbers are the height. 

How often should I replace my windows?

You should replace your windows roughly every 20 to 30 years. However, this time frame depends on the materials used for your windows, the weather conditions where you live, and the windows’ functionality. 

What's the most common window size?

The most common window size is 24 by 36 inches.


Our Rating Methodology

The This Old House Reviews Team backs up our window ratings and recommendations with a detailed rating methodology to objectively score each provider. We conduct research by speaking with company representatives, browsing product selections, analyzing window line specifications, and conducting focus groups and consumer surveys. We then score each provider against our review standards for window variety, value, trustworthiness and transparency, window features, and customer service to arrive at a final score on a 5-point rating scale. 

To share feedback or ask a question about this article, send a note to our Reviews Team at reviews@thisoldhousereviews.com.