Window Area Calculator
Calculate gross opening area, estimated glass area, total perimeter, sealant length and glazing cost for identical windows.
Default project preview
120 ft²
Estimated glass area
102 ft²
Glass order area
107.1 ft²
Total perimeter
108 ft
Area per window
20 ft²
Calculator
Build the material order
Your order will appear here
Enter the project details and calculate a rounded material estimate.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Gross area = width × height × quantity. Estimated glass area applies the frame deduction. Perimeter = 2 × (width + height) × quantity.
BuildMeter Guides
Understand the measurements and assumptions
Use these visible reference guides before changing project inputs or planning allowances.
FAQ
Window Area Calculator questions
Is rough-opening size the same as window size?+
Not always. Rough openings include installation clearances and must follow the window manufacturer specification.
Why deduct frame area?+
The frame and sash occupy part of the gross rectangular opening, reducing visible glass area.
Can this determine energy performance?+
No. U-factor, solar heat gain, glazing type and installation quality determine thermal performance.