Inverse Square Law - In an Arc Flash, Distance is your Friend

Provided for Educational Purposes Only

Contact a qualified engineer to calculate arc flash hazards.

Estimating the Arc Flash Values at Different Distances

Cals₂ = Cals₁ x (D₁/D₂)²

Calculating Arc Flash Boundary Distance, where cal/cm² is ≤ 1.2

D₂ = D₁ x √(Cals₁ / 1.2)

cal/cm² (Cals₁)
Original Distance, Inches (D₁)
New Distance, Inches (D₂)

Educational Notes & Engineering Limitations:

• Open-Air Model Only: This tool demonstrates general wave physics (1/D²). Metal enclosures direct blast energy outward, "Arc in a Box", causing real-world arc flash energy to drop off more slowly than this formula shows.
• Plasma Cloud Boundary: Working distances under 18 inches (305 mm) enter the plasma cloud, making theoretical radiation formulas invalid.
• Do Not Alter PPE: Always follow equipment arc flash labels and NFPA 70E requirements. Do not use this tool to determine PPE levels or safe work boundaries.
• Arc Blast Hazards: Distance reduces thermal burn risks, but arc blast pressure waves and shrapnel remain severe hazards during an electrical fault.