How to Use the Curtain Wall Glass Unit Calculator
Curtain wall systems are built from standardized glass units manufactured to a fixed size, so knowing your total facade area isn't enough to place an accurate order — you need the actual unit count. This calculator takes your facade area and the width/height of one unit, applies a waste factor, and gives you the number of units to order.
The math first finds the area of one unit in square feet, then divides the waste-adjusted facade area by that value and rounds up. Spandrel sections (opaque panels covering floor slabs) can be folded into the same facade area if they share the same unit size as the vision glass; if the sizes differ, calculate each section separately for accuracy.
Your waste factor should account for breakage during shipping and installation, plus cutting loss at corners and openings. A flat, standard facade typically needs only about 5%, while curved facades or ones with many window openings carry higher breakage risk and should use 10% or more to stay safe.
Frequently Asked Questions
This calculator divides total facade area by the area of one unit, so spandrel sections (opaque panels covering the floor slab) can be included as long as they share the same unit size as the vision glass. If sizes differ, calculate each section separately.
A flat, standard facade needs only about 5%. Curved facades or ones with many corners and window openings should use 10% or more to cover breakage and cutting loss.