How to Measure Windows for Replacement

If you’re going to install replacement windows, it pays to measure windows correctly the first time and avoid the headache of placing an incorrect order.

How to Measure Windows 101:

1. Always measure the entire window, not just the glass. This includes the frame and trim as well as the window glass.
2. When recording measurements, follow the format “width by height.” For example, a window that is 63 inches wide and 27 inches tall is recorded as “63 x 27.” A window that is 37 inches wide and 55 inches tall is recorded as “37 x 55.” Record your measurements to the nearest 1/16 inch.
3. Measure window width from the left edge to the right edge. Check this measurement in three places: the bottom, middle, and top. If these measurements are not equal, use the smallest as your width.
4. Measure window height from the top edge to the bottom edge. Check this measurement in three places: on the left side, middle, and right side. If these measurements are not equal, use the smallest as your height.
5. Take an additional set of measurements inside the window frame.
6. Measure the width of the trim that surrounds the window. The trim on the sides may be different from the top and bottom – so measure each part.
7. Measure the height and depth of the sill. If your windows don’t open, check if you have a door in the same wall where you can measure the wall’s thickness.
8. Take a picture of a multi-paned window and record the measurements on the print to eliminate confusion. Record the overall window width and height, both inside and outside the frame. Measure and record the width and height of each window section and the measurements of any subsections. For example, the overall window may be 60 x 20, composed of two windows 30 x 20.

What’s the Next Step?

Bring your measurements and photos into GNH and talk to one of our window experts to help plan your replacement window order. Keep in mind that the windowsill’s height may be added to your window height to get the full size of the opening. When ordering replacement windows, we recommend ordering just slightly smaller than the opening. This allows for leveling and the application of sealant.

A helpful overview of the window replacement process from Marvin Windows: