Solar Array Area Calculator
Estimate solar-panel count, DC array size, module area, spacing footprint, required usable roof area and panel cost.
Default project preview
20 panels
Module surface area
418.4 ft²
Layout footprint
451.9 ft²
Gross roof area needed
602.5 ft²
Area per panel
20.92 ft²
Calculator
Build the material order
Your order will appear here
Enter the project details and calculate a rounded material estimate.
Input and output guide
What each value means
The labels and units below are part of this calculator’s visible methodology. Replace every default with measurements or product data from the actual project.
Target DC array size
Enter this project assumption in kW. The current imperial default is 8 kW.
Panel rating
Enter this project assumption in W. The current imperial default is 400 W.
Panel length
Enter this project assumption in in. The current imperial default is 67.7 in.
Panel width
Enter this project assumption in in. The current imperial default is 44.5 in.
Layout spacing allowance
Enter this project assumption in %. The current imperial default is 8 %. Minimum: 0. Maximum: 40.
Usable roof fraction
Enter this project assumption in %. The current imperial default is 75 %. Minimum: 1. Maximum: 100.
Price per panel
Enter this project assumption in a unitless value. The current imperial default is 220. Minimum: 0.
How to read the outputs
Module surface area
panel rectangles only. Default preview: 418.4 ft².
Layout footprint
spacing allowance included. Default preview: 451.9 ft².
Gross roof area needed
75% usable fraction. Default preview: 602.5 ft².
Area per panel
entered dimensions. Default preview: 20.92 ft².
Capacity above target
whole-panel rounding. Default preview: 0 kW.
Panel cost
modules only. Default preview: $4,400.00.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Panels = round up (target kW × 1000 ÷ panel watts). Module area = panels × panel length × panel width. Layout spacing and usable-roof fraction expand the required footprint.
FAQ
Solar Array Area Calculator questions
Why is gross roof area larger than panel area?+
Spacing, setbacks, obstructions, access paths and roof geometry prevent full surface coverage.
Does roof orientation affect the geometric area?+
Orientation affects production and layout, while the basic panel rectangle area remains the same.
Can this confirm a roof can support solar panels?+
No. Structural capacity, attachment, wind and roof condition require professional evaluation.