How to Measure a Window for Replacement: 7 Tips You Should Know

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8/9/2023 Mystro Windows & Doors Canada

How to Measure a Window for Replacement: 7 Tips You Should Know

Are you considering replacing the windows in your home? Whether you're looking to improve energy efficiency, enhance curb appeal, or simply upgrade the look of your living spaces, measuring for replacement windows is a crucial first step in the process.


Measuring for replacement windows isn't rocket science, but it does require precision. Ensuring a seamless and successful window replacement process requires accurate measurements. In this article, we'll guide you through seven essential tips to ensure accurate measurements. By following these steps, you'll be well on your way to selecting and installing replacement windows that perfectly fit your home's unique architecture and style.


Keep a Precise Record

Achieving accuracy while measuring for replacement windows is key—you'll save yourself both time and money by nailing it on the first go. Regardless of whether you're replacing a single window or overhauling your entire home's windows, diligently jot down measurements as you go.


Before starting the measurement process, ensure you have the necessary tools at your disposal. A quality tape measure, a level, a pencil, and paper for jotting down measurements are your best friends for this first step. If you're ordering multiple windows, don't forget to label each set of measurements with a specific location, such as "Kitchen Window Facing North" or "Master Bedroom Window Southwest-Facing."


Measure Window Width

Accurate measurements of both width and height are critical for properly fitting replacement windows.


Measuring window width involves three points: the bottom, the middle, and the top. For accurate measurements, position your tape measure flush against the window jamb on both sides. The jamb acts as the vertical board guiding the window sash's movement as you open and close the window. To measure the bottom width, slide the window upwards and gauge the distance between the jambs at the lowest point. For the middle width, push the window all the way open and measure between the jambs near the center. For the top width, shut the window and measure between the jambs at the highest point. Record these measurements and highlight the shortest one for reference.


Measure Window Height

Sizing up the replacement window's height mirrors the width measurement approach. Again, you'll need three measurements, each spanning from the top horizontal board above the window (known as the head jamb) to the bottom sill. Capture one measurement on the extreme left, another on the far right, and a third right in the middle.


For accurate results, remember that the sill constitutes the horizontal board beneath the window sash's closed position. It's distinct from the horizontal trim board extending into the room, often referred to as the "windowsill"—though it's technically the "stool" of the window. You'll need to open the window to access the genuine sill. Record all three height measurements and accentuate the shortest one.


Consider Window Style

Different window styles have unique measuring requirements. For instance, casement windows have specific clearance needs for proper operation, while double-hung windows require measurements that account for the sashes. Take into consideration the window style you desire and research its measurement specifications to ensure a seamless fit.


Account for Installation Clearances

When measuring, remember to include allowances for installation clearances. These clearances account for the necessary space needed to properly install the window frame, insulation, and other components. Failing to consider these clearances could result in windows that do not fit snugly or function correctly.


Check for Squareness

Before finalizing your replacement window measurements, check the squareness of your existing window openings. Measure the diagonals from corner to corner, and if the measurements are equal, your window openings are square. If they are not equal, use the larger diagonal as your reference when ordering replacement windows.


Work with Professionals

While DIY measurements are possible, collaborating with professional window replacement experts can provide added assurance and accuracy. You can choose to purchase replacement windows online or from a local home improvement store. While some home improvement centers, like The Home Depot, may stock a limited selection of replacement windows on their shelves. Just keep in mind that an off-the-shelf window might come close in dimensions, but achieving a perfect fit is rare.


It's often wiser to have a customer service representative who has the experience and knowledge to handle intricate measurements. Place a custom order based on precise measurements, ensuring that your replacement windows fit perfectly and perform optimally.


Measuring replacement windows is a crucial step in ensuring a successful home improvement project. If measuring replacement windows seems challenging for you, consider seeking advice from a professional window expert like Mystro. Our window experts can provide precise measurements and recommendations based on your home's specific needs.

Read more blogs from Mystro:

6 Signs It's Time for a Door Replacement

Why You Should Replace Your Windows and Doors: Here Are The 6 Benefits You Should Know

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