How to Measure

NOTE: For a downloadable PDF of these instructions, CLICK HERE.

eGlass Windows are ordered according to the FRAME size of the window, which is the tip-to-tip dimension of the window itself. To ensure a proper fit, you must determine the ROUGH OPENING dimensions. The rough opening is the minimum amount of space needed between the window and the building structure. Be sure that the FRAME dimensions are from ½” to 1” smaller in width and height than the ROUGH OPENING dimensions.


Tape Measure • Pen or Pencil • Paper or Notepad (optional; for jotting down measurements) • A Ladder(optional; if the window is too tall to reach easily)

  • STEP 1: Clear the window area: Remove any curtains, blinds, or other obstructions that might interfere with your measurements.

  • STEP 2: If replacing an existing window (for a new opening, skip this step): Remove any trim or casing surrounding the window to expose the rough opening and to give you a clear view of the existing window frame.

  • STEP 3: Measure the WIDTH: (See Diagram A)

Starting from the inside of the opening, measure the width horizontally from Jack Stud to Jack Stud at three points: top, middle, and bottom. Record the measurements in inches.

Use the smallest of these three measurements. This ensures that the window will fit securely.

  • STEP 4: Measure the HEIGHT: (See Diagram B)

Measure vertically from the top of the rough Window Sill Plate to the bottom of the Header in three points: left side, center, and right side.

Again, record the measurements and use the smallest of these three measurements.

  • STEP 5: Verify the SQUARENESS: (See Diagram C)

Measure diagonally from one top corner to the opposite bottom corner of the Jack Studs and record measurement. Repeat for the other diagonal. If both diagonal measurements are the same, the rough opening is square.

*NOTE: If the rough opening is more than ½” out of square, this will need to be considered when selecting your window size, and modifications may be needed. In this case, you’ll want to consult with and/or hire an experienced window contractor to execute the installation.

  • STEP 6: Measure the wall DEPTH: Verify that the 3¼” frame depth of the eGlass Vinyl Window will fit into the thickness of the wall.

  • STEP 7: Double-check your measurements: We recommend that you measure twice to ensure accuracy and avoid any mistakes.

  • Step 8: Select the right size eGlass Window: Once you have all the rough opening dimensions, it’s time to select your window. Make your selection(s) according to the FRAME sizes shown on the “SHOP” page of the website.

NOTE: If you don’t see a standard size that works with your rough opening dimensions, consider altering the opening during the installation to accommodate a standard size.

To order a a custom size window, email us at:

How to Order

Follow these 4 simple steps:

Step 1: Measure

Grab your tape measure and follow the step-by-step instructions above. 

If you need additional assistance, please call us at (888) 863-4527.

Step 2: Build Your Window

Go to SHOP NOW and make all of your selections. Choose size, color, configuration (portrait or landscape), and application (new construction or replacement).

Then click "Add to Cart."

Step 3: Place Your Order

You will see your total cost including tax in your shopping cart, and shipping rates will be added to your order at checkout. You can pay with any major credit card or PayPal.

Step 4: Shipping & Delivery

Your windows will be securely packaged, insured, and shipped directly to your home or business. Plus, you'll have access to easily track your order at any time.