Skip to main content
Safety Free Pro Features Available

Shock Approach Boundary Calculator (NFPA 70E)

Look up limited, restricted, and prohibited approach boundaries for shock protection from NFPA 70E Tables 130.4(E)(a) and (b)

Free shock approach boundary lookup for electricians, line workers, and safety trainers who need to know how close they can get to exposed energized parts. Enter the system voltage and whether the conductor is fixed or movable, and the tool returns the limited approach boundary (where unqualified persons must stop), the restricted approach boundary (where even qualified persons need insulated tools and shock PPE), and the prohibited approach boundary (treated the same as making contact). Covers AC systems from below 50V through 800 kV per NFPA 70E-2024 Table 130.4(E)(a), and DC systems from below 100V through 800 kV per Table 130.4(E)(b). Includes a visual concentric boundary diagram that shows all three zones around the equipment for training and job briefing use. These boundaries are about shock protection, not arc flash. Arc flash boundaries are calculated separately using incident energy or the PPE category table method.

Pro Tip: The limited approach boundary for movable conductors (like overhead lines that can sway) is larger than for fixed conductors. If there is any chance the conductor could move toward you, use the movable conductor distance. Wind, thermal expansion, and load changes all move overhead conductors.

Calculate arc flash boundaries and incident energy

Arc Flash Incident Energy Calculator →

Look up PPE category using the NFPA 70E table method

PPE Category Table Method →

Generate an energized work permit with all boundaries included

Energized Work Permit Generator →

PREVIEW All Pro features are currently free for a limited time. No license key required.

Shock Approach Boundary Calculator
Pop Out

How It Works

  1. Select AC or DC

    Choose whether the system is AC (Table 130.4(E)(a)) or DC (Table 130.4(E)(b)). Boundary distances differ between AC and DC at the same voltage.

  2. Enter System Voltage

    Enter the nominal system voltage in volts (phase-to-phase for AC). The tool finds the matching voltage range in the NFPA 70E table.

  3. Select Conductor Type

    Choose whether the exposed energized part is a fixed circuit part or an exposed movable conductor. Movable conductors have larger limited approach boundaries.

  4. Review Boundaries

    The result shows limited, restricted, and prohibited boundaries in feet and inches and meters, plus a visual zone diagram suitable for job briefings.

Frequently Asked Questions

Shock boundaries define the distance from exposed energized parts where a person could receive an electric shock. Arc flash boundaries define the distance where incident energy from an arc could cause a second-degree burn (1.2 cal/cm2). They are calculated separately and address different hazards. Both apply simultaneously.
The boundaries apply to exposed energized conductors and circuit parts. When equipment is properly enclosed with covers and doors in place, the energized parts are not exposed and the boundaries do not apply in the same way. They become relevant when you open the panel, remove a cover, or work within the enclosure.
Crossing the prohibited approach boundary is treated the same as making direct contact with the energized conductor. You need the same PPE and procedures as if you were touching it. For many voltage ranges, the prohibited boundary is measured in inches.
Disclaimer: Approach boundaries are taken from NFPA 70E-2024 Tables 130.4(E)(a) and (b). They address shock hazards only. Arc flash boundaries must be determined separately. Actual safe approach distances depend on working conditions, tools in use, and whether insulated barriers are in place. Always follow your facility's electrical safety program.

Learn More

Safety

Arc Flash Incident Energy: What the Numbers Mean and How to Get Them Right

IEEE 1584-2018 arc flash calculation explained step by step. Arcing current, incident energy, reduced current scenario, PPE categories, and practical interpretation of results.

Read Guide →
Safety

Arc Flash PPE Table Method: When to Use It and When You Can't

NFPA 70E Table 130.7(C)(15) PPE category lookup explained. When the table method works, when it doesn't, what exceeds table scope, and how to read PPE categories.

Read Guide →
Safety

Shock Approach Boundaries: Who Can Cross Which Line

NFPA 70E shock approach boundaries for AC and DC systems. Limited, restricted, and prohibited distances, who needs what training, and what PPE is required at each boundary.

Read Guide →
Safety

Energized Electrical Work Permits: When You Need One and How to Fill It Out

NFPA 70E 130.2(B) energized electrical work permit requirements. When energized work is justified, what goes on the form, and the approval process.

Read Guide →

Related Tools

Safety Live

Lockout/Tagout Permit Manager

Create OSHA-compliant LOTO permits for equipment energy isolation. Track electrical, pneumatic, hydraulic, and thermal energy sources with lock assignments and zero-energy verification.

Launch Tool →
Safety Live

Scaffold Load & Tie Calculator

OSHA 1926.451 scaffold loading calculator. Determine platform capacity, leg loads, mudsill sizing, and tie spacing for light, medium, and heavy-duty scaffolding.

Launch Tool →
Safety Live

Fire Sprinkler Hydraulic Calculator

NFPA 13 sprinkler hydraulic calculator. Compute flow using K-factor, Hazen-Williams friction loss in piping, and total system demand at the riser with hose stream allowance.

Launch Tool →