Arc Flash Boundary Calculator

Arc Flash Boundary (AFB) — the distance from a potential arc source within which a person could receive a second-degree burn — calculated per the IEEE 1584-2002 empirical model (208 V–15 kV) or the Ralph Lee (theoretical) method for higher voltages or quick estimates.

IEEE 1584-2002 Model

Lee Method (>15 kV / Quick Estimate)

Equipment / Enclosure Type Auto-fills a typical conductor gap and distance exponent (x) — both remain editable.

System Voltage (V) Model valid 208–15,000 V. Nominal system voltage, not line-to-line kV.

Bolted Fault Current (kA) Three-phase symmetrical RMS. Model valid 0.7–106 kA.

Conductor Gap (mm)

Distance Exponent (x)

Arc Duration / Clearing Time (s) Total protective device clearing time for this fault current.

Working Distance (mm) 18 in ≈ 457 mm; 24 in ≈ 610 mm.

System Grounding

Incident Energy at Boundary (cal/cm²) Standard second-degree-burn threshold is 1.2 cal/cm².

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Arcing Current (kA)

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Incident Energy (cal/cm²)

Arc Flash Boundary (mm)

System Voltage (kV)

Bolted Fault Current (kA)

Arc Duration (s)

Working Distance (mm)

Incident Energy at Boundary (cal/cm²)

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Incident Energy (cal/cm²)

Arc Flash Boundary (mm)

Formula Reference — IEEE 1584-2002

Arcing Current: log(Ia) = K + 0.662·log(Ibf) + 0.0966·V + 0.000526·G + 0.5588·V·log(Ibf) − 0.00304·G·log(Ibf) (V < 1 kV); log(Ia) = 0.00402 + 0.983·log(Ibf) (V ≥ 1 kV)
Normalized Incident Energy: log(En) = K1 + K2 + 1.081·log(Ia) + 0.0011·G
Incident Energy: E = Cf × En × (t / 0.2) × (610 / D)^x cal/cm²
Arc Flash Boundary: DB = 610 × [Cf × En × (t / 0.2) / EB]^(1/x) mm

K (arcing current)	−0.153 open / −0.097 box
K1 (incident energy)	−0.792 open / −0.555 box
K2 (incident energy)	0 ungrounded / −0.113 grounded
Cf (calculation factor)	1.5 if V ≤ 1000 V, else 1.0

Formula Reference — Lee Method

For voltages above 15 kV, or as a fast theoretical-maximum estimate: E = 793 × V × Ibf × t ÷ D² cal/cm² (V in kV, Ibf in kA, t in s, D in mm) — the theoretical maximum power condition (Ralph Lee, 1982), generally more conservative (higher) than IEEE 1584 results.

Traditional PPE Category Reference (cal/cm²)

Category 1	4 cal/cm² minimum arc rating
Category 2	8 cal/cm² minimum arc rating
Category 3	25 cal/cm² minimum arc rating
Category 4	40 cal/cm² minimum arc rating

Methodology, interpretation & sources

Purpose. Arc Flash Boundary (AFB) — the distance from a potential arc source within which a person could receive a second-degree burn — calculated per the IEEE 1584-2002 empirical model (208 V–15 kV) or the Ralph Lee (theoretical) method for higher voltages or quick estimates.

Primary references. Use the current edition/version that applies to your jurisdiction and organization:

Editorial note. Prepared and maintained by Impact Tech Solutions. Editorially updated 28 September 2026. No individual professional credential is claimed on this page; high-consequence, statutory, tax, engineering or health decisions should be independently verified against the current primary source and, where required, a qualified professional.

Arc Flash Boundary Calculator

Formula Reference — IEEE 1584-2002

Formula Reference — Lee Method

Traditional PPE Category Reference (cal/cm²)

Methodology, interpretation & sources

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