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By: Louisville Window Co.

How to Measure a Window for Replacement (DIY Guide)

two man measuring house window

Replacing a window in your home can be a rewarding DIY project that can enhance energy efficiency and aesthetics. However, before you start shopping for replacement windows, you’ll need to measure your existing windows accurately. It might seem like a daunting task, but with the right guidance, it’s a manageable DIY project. 

In this guide, we’ll take you through the step-by-step process of measuring a window for replacement, ensuring you get the right fit.

What’s inside this blog:

  • 8 steps for how to measure a window for replacement
  • Details under each step

Keep reading to become a true pro at measuring windows!

Gather Your Tools 🧰

Before you begin, make sure you have the following tools ready:

  • Tape Measure: A retractable tape measure is essential for precise measurements.
  • Paper and Pen: Keep a notepad and pen handy to jot down measurements.
  • Level: A level helps ensure that your measurements are accurate and straight.

Step 1: Measure the Width 📏

Start by measuring the width of your window. Follow these steps:

  1. Inside or Outside Frame: Decide whether you want to measure the inside of the window frame or the outside, depending on your preference and the type of replacement window you plan to install.
  2. Inside Frame Measurement: If you’re measuring the inside frame, start from the inside edge of one side to the inside edge of the opposite side. Measure horizontally at three points: the top, middle, and bottom of the window. Record the narrowest measurement of the three, as this ensures the replacement window will fit within the frame.
  3. Outside Frame Measurement: For measuring the outside frame, start from the exterior edge of one side to the exterior edge of the opposite side. Again, measure horizontally at three points: the top, middle, and bottom. This time, record the widest measurement of the three, as you’ll want the new window to cover the entire frame.

Step 2: Measure the Height 📏

Next, measure the height of your window following these steps:

  1. Inside or Outside Frame: Similar to the width, decide whether you’re measuring the inside or outside frame of the window.
  2. Inside Frame Measurement: If you’re measuring the inside frame, start from the inside edge of the top frame to the inside edge of the bottom frame. Measure vertically at three points: the left, center, and right sides of the window. Record the shortest measurement among the three.
  3. Outside Frame Measurement: When measuring the outside frame, start from the exterior edge of the top frame to the exterior edge of the bottom frame. Measure vertically at three points: the left, center, and right sides of the window. Record the tallest measurement among the three.

Step 3: Check for Squareness 📐

To ensure your window opening is square, measure the diagonals. Here’s how:

  1. Measure Diagonally: Measure from the top left corner of the window to the bottom right corner, and then from the top right corner to the bottom left corner. These diagonal measurements should be equal if the window opening is square.
  2. Adjust if Necessary: If the diagonal measurements differ by more than a half-inch, your window opening may not be perfectly square. In this case, consider adjusting the frame or consulting a professional to ensure a proper fit for your replacement window.

Step 4: Determine the Depth 📦

The depth of your window opening is crucial for selecting the right type of replacement window. Here’s how to measure it:

  1. Inside or Outside Depth: Again, decide whether you want to measure the inside or outside depth of the window frame.
  2. Inside Depth Measurement: For inside depth, measure from the interior of the window frame to the exterior of the window frame. This measurement will help you determine the thickness of the replacement window you need.
  3. Outside Depth Measurement: If measuring the outside depth, start from the exterior of the window frame to the exterior of the window frame. This measurement may be useful if you plan to install an exterior trim or storm window.

Step 5: Record and Double-Check 📝

Now that you have your measurements, record them accurately. Double-check your numbers to ensure you haven’t made any mistakes. It’s a good practice to take each measurement at least twice to confirm consistency.

Step 6: Determine the Window Style 🪟

Before you start shopping for replacement windows, consider the style you want. Here’s a numbered list of some common window styles:

  1. Single-Hung: These windows have a fixed upper sash and a lower sash that slides vertically. They are ideal for a traditional look and are energy-efficient.
  2. Double-Hung: Similar to single-hung windows, but both upper and lower sashes can be opened. They offer excellent ventilation and are easy to clean.
  3. Casement: These windows have a side hinge and open outward like a door. They provide a contemporary look and offer excellent ventilation.
  4. Slider: Slider windows open horizontally by sliding one sash over the other. They are space-efficient and provide a modern appearance.
  5. Awning: Awning windows are hinged at the top and open outward from the bottom. They are ideal for ventilation and work well in small spaces.
  6. Picture: Picture windows are fixed and do not open. They are designed to provide unobstructed views and maximize natural light.
  7. Bay and Bow: Bay windows project outward and create a cozy nook inside. Bow windows are curved and provide a panoramic view.
  8. Custom Shapes: Some replacement windows can be customized to fit unique or irregular window openings.

Step 7: Consult a Professional (If Needed) 🏡🔍

While measuring your windows for replacement is a manageable DIY task, it’s always a good idea to consult a professional if you’re unsure or if your window openings have unique features or challenges. Professionals can provide accurate measurements and guidance to ensure a smooth replacement process.

Step 8: Start Shopping for Replacement Windows! 🪟🛒

Now that you have your measurements and window style preferences, you’re ready to start shopping for replacement windows. Keep your measurements handy as you browse different options, and don’t hesitate to ask for assistance from window professionals or retailers if you have any questions.

Become a Pro at Measuring Windows

Knowing how to measure a window for replacement is an essential step to ensure a seamless and successful home improvement project. By following this DIY guide, you’ll be well-prepared to select the right replacement windows that fit your home perfectly. Whether you’re aiming to boost energy efficiency, update your home’s aesthetics, or improve ventilation, accurate measurements are the foundation for a successful window replacement project.

Contact our team of experts today and we’ll kick off your next home project with a free estimate and easy in-home consultation!

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