Ground Electrode Resistance Calculator

Measurements and entries

Record ambient temperature, bundling, insulation class, and termination conditions. Nameplate and meter values are not interchangeable unless they describe the same condition.

Values used below a division bar must stay positive. Check every prefix before entry; micro, milli, kilo, and mega are not interchangeable. If you also need internal resistance, continue with Battery Internal Resistance Calculator.

Test voltage

Default example: 25 V. Enter test voltage in V.

Measured test current

Default example: 5 A. Enter measured test current in A.

Formula used on this page

The arithmetic is based on R = V ÷ I. Only Test voltage and Measured test current enter the numerical result.

Using the loaded examples gives 5.00 Ω. Your saved case should identify where each entry came from.

Calculate estimated ground resistance from test voltage and measured test current. Another relevant worksheet is Grounding Voltage Rise Calculator.

Changing Test voltage

Change Test voltage from 25 V to 30 V with every other entry unchanged. The result changes from 5.00 Ω to 6.00 Ω.

This isolates one variable; a real system may change several at once.

Applying the result

Use Estimated ground resistance as one quantified check within the larger decision. Compare it with the applicable installation and equipment requirements.

Label alternate cases rather than overwriting the baseline.

Assumptions and limitations

Soil moisture and electrode geometry can change the reading.

Outside the entered variables, consider termination heating, installation method, ambient temperature, and grouping. Resolve material omissions before selecting a standard size or rating.

Record ambient temperature, bundling, insulation class, and termination conditions.

Before carrying the answer forward

Review measured test current and the remaining entries as one case. If one value belongs to another temperature, load, or time period, separate the scenarios.

Use estimated ground resistance alongside the selected conductor and protective-device ratings. Preserve the unrounded number until all dependent calculations and comparisons are complete.

Keep a baseline and vary the least certain measurement first. A separate analysis may be needed for fault duration, protective-device curves, and conductor thermal limits.

Before relying on the answer