Re = ρ / L
Re = 2 * (ρ / L)
Re = 2 * (ρ / P)
Re = ρ / (4 * r)
Re ≤ UL / Idn
Re = Ground resistance (Ω)
ρ = Resistivity (Ω * m)
L = Length (m)
P = Perimeter (m)
r = Radius (m)
UL = Safety voltage (V)
Idn = Tripping current (A)
This tool calculates the grounding resistance of an earthing system based on soil resistivity, electrode type, and geometric parameters. It helps verify compliance with IEC 60364-4-41 for coordination between earth electrodes and residual current devices (RCBOs).
The calculated resistance is compared to the safety voltage limit (typically 50 V or 25 V) to ensure safe operation and proper tripping of protective devices.
• Type of ground electrode – Physical form of the grounding element:
Rod
Horizontal rope
Ring
Mesh network
• Soil Type – The type of soil where the electrode is installed. Used to estimate resistivity (ρ). Typical values:
Agricultural: 10–150 Ω·m
Sandy gravelly: 50–300 Ω·m
Clay: 50–200 Ω·m
Marine sands: 200–3000 Ω·m
Rocky: 1500–10000 Ω·m
Custom: User-defined value
• Quantity (n) – Number of parallel grounding electrodes used.
• Length (L) – Total length of the grounding conductor in meters.
For Rod: depth of the vertical rod
For Horizontal rope: total length of the conductor
For Ring: circumference of the ring
For Mesh network: total length of all buried conductors
• Resistivity (ρ) – Soil resistivity in ohm-meters (Ω·m). If not measured, use typical values from soil type.
• Safety Voltage – Maximum allowable touch voltage:
50 V: Normal dry environments
25 V: Wet, confined, or high-risk locations
Usage Tip:
Enter the parameters and calculate the grounding resistance. Then check if:
R ≤ U₀ / IΔn
Where:
R = Ground resistance (Ω)
U₀ = Safety voltage (50 V or 25 V)
IΔn = Rated residual operating current of RCBO (e.g., 0.03 A for 30 mA)
Example: For 30 mA RCBO and 50 V safety limit:
R ≤ 50 / 0.03 ≈ 1667 Ω → System is acceptable if R < 1667 Ω.
This calculator complies with IEC 60364‑4‑41. It calculates resistance for rod, horizontal, ring and mesh grounding systems.
It verifies coordination between earth electrodes and RCBO residual current devices based on safe touch voltage limits for residential and industrial earthing design.
Soil resistivity is the dominant factor of earthing performance. Dry, sandy or rocky soil has high resistivity and poor grounding effect.
You can use built‑in soil type presets for estimation. For precise engineering design, field‑measured resistivity data is required.
Parallel‑arranged ground electrodes reduce total grounding resistance. However, shielding effect prevents proportional resistance reduction with electrode quantity.
Sufficient spacing between electrodes is required for effective resistance reduction. This calculator takes electrode count n to estimate resistance of parallel earthing arrangements.
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