How to Measure a Window for Glass Replacement
The major and crucial step in window replacement glass is window measurement. People usually ask, “How to measure for replacement windows?” but they do not get satisfied by the answers.
Keeping in view the user problems, Fab Glass and Mirror has opted to enlighten people about measuring the replacement glass for windows efficiently. Read our expert guide on taking the correct measurements for replacement windows and avoid any inconvenience.
The first and foremost thing is to know the size of your window. Taking the accurate and precise measurements of the window you would like to replace is the best thing you can have. So, let’s dig out the measurement guide.
Table of Contents
Step 1: Take Horizontal Measurements
While taking the dimensions of the replacement window, always measure it at three points. It gives a clear insight into whether the window has equal distances or not. Take the horizontal measurements from the top, middle, and bottom.

- Take the measurements of the top side first with the help of measuring tape. Measure from one jamb surface to the other
- Measure from the middle and then the bottom of your window
- Now you have three measurements of your window. Use the smallest measurement as your width dimension.
Step 2: Take Vertical Measurements
You have to repeat the same measuring steps of width measurement while taking vertical dimensions i.e. three measurements vertically (leftmost, middle, rightmost).
- Measure the height distance across the window frame from bottom to top from left, middle, and right of the window from the window sill to the head jamb.
- Just like the width measurement, take the smallest measure of the height while ordering your replacement window.

FYI: What is the subtract factor in window measurements?
You might have heard about subtracting something from the final measurements of windows for glass replacements. That’s rubbish, and don’t ever do this at all. While ordering for glass replacement, only provide the opening size of the window. Just order with the right measurements and let it be the manufacturer’s headache.
Step 3: Take Depth Measurements

Finally, the depth is the last thing of a window to measure for glass replacement. After taking the depth dimensions, you are all set to order a glass replacement for yourself.
- Measure the depth from the inside window trim to the outside blind stop strip.
- Take the dimensions of the depth from several points.
Note: Don’t worry about the pulleys and parting strips while taking depth measurements. All this stuff is removed during window installation.
Rough Opening and Window Size
The rough opening is the opening where the window frame sits. The rough opening measurements are important while choosing a frame size. However, the replacement window size is lesser than the rough opening as the frame has a header, sill, and vertical trimmers.
You Can Take Measurements in Square Feet Too
If the above-given steps don’t make you feel at ease, you may opt to measure the window for glass replacement in square feet.
- Measure (in inches) across the bottom of the window glass
- Measure from bottom to top
- Multiply both readings and divide them by 144 to have the measurements in square feet
Note: The window glass area is calculated by multiplying the length into width.
What is the standard size for a window?
People usually ask for the standard window size. For their information, there is no particular standard measurement of a window. Yes, it’s a sure thing that when you shop for replacement windows, you probably encounter some consistent size dimension windows. These windows are made to fit mostly the rough opening sizes in the home. However, it’s always better to measure your windows and place an order. If you don’t find a pre-manufactured window, you’ll have to go for a custom-cut solution.

Talking about the common window size usually found at home is 24✕36. You can’t take it as a standard size but a common size.
Pro Tip: Fab Glass and Mirror is in favor of performing DIY tasks at home. However, for window measurement, we highly encourage you to get the help of professionals to ensure error-free measurements of your replacement window glass. This step will avoid you from financial loss as well as give you peace of mind.
Where to Buy High-Quality Replacement Glass?
The glass market is very diverse, and you find several types of glass for windows. The important thing is the quality of the replacement glass and its price. At Fab Glass and Mirrors, we offer a wide range of replacement glass of different shapes, sizes, and finishes. Order online a high-quality replacement glass at a reasonable price.







