Lightning Protection Calculator

Air terminal and conductor layout per NFPA 780 from building dimensions and roof type.

Roof length (ft)

Roof width (ft)

Building height (ft)

Roof type (1=Flat, 2=Gable, 3=Hip)

Class (1=Standard, 2=Enhanced)

Tab to move between fields

Total air terminals

Perimeter terminals13

Interior/ridge terminals6

Down conductors4

Ground rods4

Total conductor (ft)1,120

Roof area (sq ft)6,000

Perimeter (ft)320

Conductor Spec2 AWG copper

Ground Rod Spec5/8" × 10 ft copper-clad steel

How to Use This Calculator

Enter the roof length and width in feet from the building's floor plan.
Enter the building height in feet from grade to the roof peak or parapet.
Select the roof type: flat (1), gable/ridge (2), or hip (3) to determine air terminal placement.
Select the protection class: standard Class I (1) for ordinary structures or enhanced Class II (2) for high-value buildings.
Read the total air terminal count, down conductor count, ground rod count, and total conductor footage needed.

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