Before ordering or buying windows for replacement, it’s important to get accurate measurements. This is because one wrong measurement means ordering the wrong size window, which will cost both your time and money.
Measuring windows is a simple DIY task. This blog will walk you through a few essential steps to get your measurement right.
Get to Know Your Window Parts
Windows come in different styles and sizes, but their basic outline will usually remain the same. Knowing the key window parts will help when buying a window replacement, as window manufacturers often use these terms to refer to window measurements.
The following are a few window terms that are used in measuring:
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Sash: This part of the window holds the glass. It could be either fixed or movable.
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Head: This is the top horizontal part of the frame, which touches the top of the sash.
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Sill: This is the bottom horizontal part of the frame, which touches the bottom of the sash.
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Jambs: They are the vertical pieces on both sides, which touch the sides of the sash.

Measure the Width
Window sizes are always referenced by the width first, and then the height (Width x Height). Width should be measured from jamb to jamb. For more accuracy, measurements should be taken at three different points: the top, middle, and bottom.
This will give you the average measurement of the window width. Also, all three spots should be measured at the widest point possible to help you deduce what the actual window size was.
Measure the Height
For height, measure from the high point of your window sill to the top of the window opening. Here, make three vertical measurements: one at the left side of your window, the center, and the last one at the right side. It is very important to use the smallest of these three measurements while ordering the window.
Measure the Depth
After width and height, it is time to measure the window’s depth. This measurement goes from the inside face of the interior stop to the inside face of the exterior stop. While taking depth measurement, ignore all the pulleys and parting strips. They are usually removed for replacement window installation.
To accommodate a replacement window, there should be a minimum depth of 3-1/4 inches between the interior stop and the exterior stop.
Check for Square, Level, and Plumb
It is also very important to know if your existing window frame is square, level, and plumb. Replacements are often square, with 90-degree corners. Plumb measures the vertical straightness, and level measures the horizontal straightness.
For Square: Measure diagonally from the top right corner to the lower left corner, where the trim meets. Next, measure from the top left corner to the lower right corner. If the measurements are within ¼ inch of each other, then most standard-size windows will fit in your window opening.
For Plumb: To measure this, place the level against the face of the side jamb. If the bubble is between the two indicator lines on the level, your window is plumb.
For Level: Start by placing the level on the sill. If the bubble is between the two indicator lines on the level, your window is level.
Tips to Measure More Accurately
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Always make sure to measure between the jambs. This measurement should not include any trim or decorative elements.
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Overlooking depth measurement may not be a good sign while looking for a replacement. There should be at least a minimum of 3 ¼ inches of depth for a smooth fit.
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As mentioned above, width and height should be measured in three points. In this, the smallest measurement of the three should be used while ordering.
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Make sure to remove jamb liners or parting strips before going ahead with the measurement.
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If it is a bay window or bow window, make sure to measure each panel. This will take into account the unique angles and shapes.
Different Types of Replacement Windows
While replacing the windows, you can always get creative with the type of window you are replacing. This new replacement might be completely different from your old window. Here are a few common types of replacement windows that you can choose from.
Double Hung Window

They are the most common type of window available on the market. A great perk of choosing this type is increased airflow and ventilation. Their tilting sashes also make it easier to clean.
Sliding Window

They come in two or three-panel setups and have one or two movable panes. These windows are horizontally oriented, therefore fitting in anywhere with a panoramic view.
Awning Window

They work by cranking them open from the bottom, while the top edge is fixed. During rain, they can be kept open with the glass serving as an ‘awning’. This prevents the water from getting in.
Picture Window

They are ideal for places where you need more light, but not necessarily extra ventilation. They also come in specialty shapes to provide a unique touch to your space.
Conclusion
Getting accurate measurements of your window will lead to a successful replacement; therefore, sufficient time should be taken to measure the window. If this DIY process of measuring seems complicated to you, do not hesitate to contact professionals who are trained to replace windows with higher levels of accuracy..