Enter the total glazing window area and the total wall area into the calculator to determine the window to wall ratio and the wall to window ratio.

Window to Wall Ratio Formula

The following equation is used to calculate the Window to Wall Ratio.

  • Where WtWr is the window to wall ratio
  • GWA is the glazing window area (ft^2)
  • GEWA is the gross exterior wall area (ft^2)

To calculate a window to wall ratio, divide the glazing window area by the gross exterior wall area.

What is a Window to Wall Ratio?


A window to wall ratio is a measure of the amount of window area there is on a building relative to the total amount of exterior wall area.

The most efficient window to wall ratios are those of approximately 20% window to wall area.

How to Calculate Window to Wall Ratio?

Example Problem:

The following example outlines the steps and information needed to calculate Window to Wall Ratio.

First, determine the total glazing window area. In this example, the total window area is measured to be 150 ft^2.

Next, determine the total wall area. For this building, the total wall area is found to be 1000 ft^2.

Finally, calculate the window to wall ratio using the formula above:


WtWr = 150 / 1000

WtWr = .15 = 15%