Guide To Measuring For Replacement Windows: Step-by-Step

December 17, 2009

A primary consideration when measuring for replacement windows is whether you plan on installing into a rough frame or using the existing window frame. Because not all window sizes are available from your local home center, you may end up having to remove the existing frame in order to keep costs down. Here's how to measure for replacement windows.

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Step 1. Measure the width of the window at three points--left, middle and right. Always use the shortest measurements of the three to insure proper fit. For example, if you install a bay window and you use the larger of the measurements, the window will not fit into the opening. However, a window that has some space between it and the frame can be shimmed and caulked.

Step 2. Measure the height of the window at the same three points--left, middle and right. Again, take the smallest of the measurements just to be safe. A word on measurement discrepancies: one-quarter to one-half inch longer than the actual measurement is the rule of thumb. Never, ever be short.

Step 3. Find someone else to conduct the same measurement procedure. You could be off for a number of reasons and not even know it. Compare the measurements for continuity before taking them to the home improvement center for ordering.

Step 4. Discuss your measuring procedure with the window professional at the home center. Tell them exactly how you arrived at your measurements as well as any other peculiarities of your windows. If you plan on installing a bay window, check with the window pro for additional considerations.

Knowing how to measure for replacement windows is a simple process that requires just a little common sense and some practice. But it is a critical part of the process.


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