How to Calculate Window Trim
- 1). Measure the outside perimeter of one window with a tape measure. It's usually easiest to measure the height and width of the window, then multiply by 2, since the height and width are typically identical on both sides.
- 2). Measure the perimeter of the remaining windows.
- 3). Add the measurements of all the windows. Multiply the total by 1.2, to account for the possibility of 20 percent wasted material during cutting and installation.
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