Step and Touch Voltage Calculator — IEEE 80

Calculate tolerable step and touch voltages from fault duration, surface resistivity and body-weight curve, with optional estimates from grid potential rise.

Step & Touch Voltage — IEEE 80 Calculator

Calculate tolerable touch and step voltage limits using the IEEE 80 equations for 50 kg or 70 kg. Optional GPR fractions are illustrative estimates, not a grounding-grid safety assessment.

Standard / Method: IEEE Std. 80 (direct method)Body weight (kg): 70 kg curve50 kgCustom weight (kg): Fault clearing time (s): Surface layer resistivity ρs (Ω·m): Surface derating factor Cs: No surface layer (Cs = 1)Example factor: Cs = 0.5Example factor: Cs = 0.3Enter custom Cs Cs (custom): Grid Potential Rise (GPR) — V: Symmetrical fault current before Sf and Df (A): Grid resistance Rg (Ω): Decrement factor Df: Current division factor Sf: Estimate – step fraction (if GPR used): Estimate – touch fraction (if GPR used):

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Item	Value

How are limits calculated?

Ib = k / √t; Etouch = Ib × (1000 + 1.5 × Cs × ρs); Estep = Ib × (1000 + 6 × Cs × ρs). Use k = 0.116 for 50 kg or 0.157 for 70 kg. This calculator implements the IEEE equations only; it does not implement IEC 60479 or an arbitrary body-weight curve.

How should I use the GPR estimate?

Enter measured or separately calculated GPR, or calculate GPR from fault current × Sf × Df × grid resistance. Do not apply Sf and Df twice. Step and touch fractions are user assumptions, not values derived from electrode geometry. Site measurements and a full grounding study are required for a safety assessment.

Worked examples

Use seconds for fault duration, Ω·m for surface resistivity and a dimensionless surface factor Cs. With t = 1 s, ρs = 100 Ω·m and Cs = 1, the 70 kg curve gives Ib = 0.157 A, touch voltage = 180.55 V and step voltage = 251.20 V. Selecting the 50 kg curve gives 0.116 A, 133.40 V and 185.60 V.

As an arithmetic example, 10,000 A × Sf 0.5 × Df 1 × Rg 0.2 Ω gives GPR = 1,000 V. User-selected fractions of 0.2 for step and 0.3 for touch produce estimates of 200 V and 300 V. Those fractions must come from a separate analysis; changing them cannot establish that an installation is safe.

Scope and reference

The calculation gives tolerable voltage limits under the selected assumptions. It does not model soil layers, electrode geometry, mesh voltages, transferred potentials or local compliance. Confirm applicability and fault-duration limits against the edition used for the project, and obtain a qualified grounding review before using results for an installation.

The equations and a numerical example are reproduced in Appendix B of “Numerical Simulation of Potential Distribution in Grounding Systems” (Energies, 2025), which cites IEEE Std 80.