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How to Measure Windows for Replacement

Window Image

Save yourself time and expense by getting correct measurements before ordering your replacement windows.


Measuring the Window Opening

Take the following measurements for each window you plan to order, and a customer service associate at Lowe’s will help you find the correct size windows for your openings.

To Measure Width:

Measure between the jambs at three points: top, middle and bottom of the window opening. Measure from the surface of the jambs, not from the trim strips or parting beads in your old window opening. Use the smallest of these three measurements to order the window.

To Measure Height:

Measure from the high point of the sill of your window (the surface closest to the inside of the window) to the top of the window opening. Make three measurements: one at the left side, one at the center and one at the right side of the window. Use the smallest of these three height measurements to order the window.

To Measure Depth:

Ignore all pulleys and parting strips when measuring for depth dimensions, as they'll be removed for replacement window installation. There must be at least 3 1/4 inches of opening depth between the inside window trim and the outside blind stop strip. This much area is necessary to accept the depth of the replacement window.



Ordering Your Windows

When you order windows, provide the opening size only. The manufacturer will deduct the following: 

  • After ¼-inch deduction widths will be cut to the nearest 1/8-inch increment.
  • After ¼-inch deduction heights will be cut to the nearest 1/8-inch increment.