Arc-Flash Incident Energy Calculator

An arc flash does not have to be slow to be deadly. Vaporized copper expands, plasma reaches thousands of degrees, and the heat reaches a worker in the same breath as the light. The number that matters is incident energy - cal/cm² at the body.

Arc-Flash Incident Energy Calculator produces an IEEE 1584-style estimate of incident energy, the flash hazard boundary, and a PPE category band from the fault current, clearing time and distance.

It is an orientation tool. PPE and labels must come from a formal arc-flash study and the standard in force.

• Fault current: kA at the bus, from the fault study.
• Clearing time: The protective device opening time.
• System voltage: LV network, typically 208-600 V.
• Working distance: How far the worker stands.
• Incident energy: cal/cm² computed directly.
• Boundary: Distance to 1.2 cal/cm².
• Category: PPE band suggestion.
• Export: Copy or download as text, CSV or JSON.

1. Enter the bolted fault current at the bus (kA).
2. Enter the device clearing time in seconds.
3. Set the system voltage and phase.
4. Set the working distance in inches.
5. Read the incident energy and hazard boundary.
6. Choose PPE with an arc rating above the energy.

Example 1 — Fast 480 V panel. 20 kA cleared in 0.1 s at 18 in: about 2.9 cal/cm² - Category 2 territory.

Example 2 — Slow feeder. 30 kA cleared in 0.5 s at 18 in: near 16 cal/cm² - a Category 4 hazard that demands a full study.

Example 3 — MV bus. 25 kA at 11 kV with a 0.2 s trip: far higher energy - MV work needs its own method and study.

• Energy visible: cal/cm² from real inputs.
• Boundary known: Where 1.2 cal/cm² lies.
• PPE oriented: Category band suggested.
• Time shown: Why fast clearing matters.
• Private: No uploads, no accounts, no logging.