Grounding System Calculator

Design grounding electrode systems: calculate single rod resistance, parallel rod resistance, touch and step voltages.

Soil Resistivity

Ω·m

Rod Length

Rod Diameter

Number of Rods

rods

Rod Spacing

Tab to move between fields

System Resistance

17.63 Ω

Meets 25Ω Limit?

1 (1=yes, 0=no)

Single Rod Resistance33.49 Ω

Touch Voltage (est.)12,339.41 V

Step Voltage (est.)5,288.32 V

How to Use This Calculator

Enter the Soil Resistivity in Ω·m — measure with a four-point (Wenner) test or estimate from soil type: clay ≈ 40, loam ≈ 100, sand ≈ 1,000.
Enter the Rod Length in meters — NEC minimum is 2.4 m (8 ft); 3 m (10 ft) rods are standard.
Enter the Rod Diameter in mm — standard sizes are 16 mm (5/8") or 19 mm (3/4").
Enter the Number of Rods and the Rod Spacing in meters — rods should be spaced at least 1× their length apart for effective parallel operation.
Read the System Resistance in Ω — NEC recommends below 25 Ω; utility and sensitive equipment installations often require below 5 Ω.
Review estimated Touch Voltage and Step Voltage to identify safety concerns and whether additional rods or a ground ring is needed.

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