What standard does this calculator follow?

It uses the legacy IEEE 1584-2002 empirical equations with the enclosed-equipment constant (K = −0.097), grounded-system energy constant (k2 = −0.113), and switchgear distance exponents. The 2018 revision uses a substantially different model with additional inputs. This tool is suitable for preliminary estimates only.

What is incident energy?

Incident energy is the amount of thermal energy (cal/cm²) impressed on a surface at a given working distance from an arc flash event. Under NFPA 70E §130.5, when using the incident energy analysis method, PPE must be selected based on its arc rating (cal/cm²) meeting or exceeding the calculated incident energy, rather than using prescriptive PPE categories.

What is the arc flash protection boundary?

The arc flash protection boundary (AFB) is the distance from the arc source at which the incident energy equals 1.2 cal/cm² — the threshold for a second-degree burn on unprotected skin.

What electrode gap should I use?

IEEE 1584-2002 Table 4 lists typical gaps of 32 mm for low-voltage switchgear, 102 mm for 5 kV switchgear, and 152 mm for 15 kV switchgear. Use the preset buttons or enter the gap established for the equipment being assessed.

How accurate is this calculator?

IEEE 1584-2002 equations are empirical and have ±20% accuracy. Use this tool for planning and training only. A full arc flash study by a licensed engineer is required for NFPA 70E compliance.

What does the arcing current multiplier do?

For systems at or below 1 kV, IEEE 1584a-2004 introduced an 85% arcing-current check because a lower current can make the protective device operate more slowly. When using 0.85, enter the clearing time that corresponds to that reduced current; keeping the same time will only show the energy effect of the lower current.

Arc Flash Calculator

Estimate arc flash incident energy (cal/cm²) and protection boundary for enclosed, grounded equipment using the IEEE 1584-2002 model.

System Parameters

System Voltage (V)

Range: 208 – 15,000 V

Bolted Fault Current (kA)

Three-phase symmetrical RMS (0.7 – 106 kA)

Electrode Gap

Working Distance (mm)

Typical: 455 mm (low-voltage panel), 610 mm (switchgear)

Fault Clearing Time

6 cycles = 0.1 s at 60 Hz

Arcing Current Multiplier

Enter system parameters and press
Calculate Arc Flash to see results.

Summary

This arc flash calculator applies the legacy IEEE 1584-2002 empirical equations for enclosed, grounded switchgear to estimate incident energy at a given working distance and the arc flash protection boundary. Enter system voltage, bolted fault current, gap between conductors, working distance, and clearing time to get a preliminary result in cal/cm².

How it works

Enter the system voltage (208 V – 15,000 V) and electrode gap for your equipment type.
Enter the bolted three-phase fault current available at the point of work.
Set the arcing current multiplier and the fault clearing time in cycles or seconds.
Set the working distance from the potential arc source to the worker.
The calculator computes arcing current, normalized incident energy, and final incident energy.
The arc flash boundary is found by back-solving for the distance at the 1.2 cal/cm² onset-of-ignition threshold.

Use cases

Perform a preliminary arc flash hazard assessment before a full IEEE 1584 study.
Determine the required minimum PPE arc rating (cal/cm²) for switching or racking operations.
Estimate how changing clearing time affects incident energy at a switchgear panel.
Verify that an upstream breaker provides adequate arc flash protection.
Train electricians on the relationship between fault current, distance, and incident energy.
Compare incident energy for different working distances during maintenance planning.

Frequently Asked Questions

Last updated: 2026-05-28 · Reviewed by Nham Vu