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What is the mathmatical formula for calculating the resistance-to-ground of parrallel electrodes?

Hi Slamat,

Thank you for your question regarding resistance-to-ground calculations for parallel electrodes, it is our pleasure to help.

The simplified calculation for predicting the resistance-to-ground (earth) of a given length grounding rod is:

R=(p/(2*pi*L))*(ln*(4L/a)-1)) + (p/(2*pi*s))*(1-(L squared/3s(10X8)) + (2L(10×4)/5s(10×4)…)


  • R= Resistance
  • p= soil resistivity
  • L = Length of the rod
  • a= radius of the rod
  • ln= natural log
  • s = rod spacing

The above is the hand formula, however it does not take into account multi-layered soils.  We highly recommend using a computer program such as CDEGS.  Here are a few other links that you may find useful:



We hope you find this information useful.  If you should have any further questions. Please do not hesitate to contact us again in the future.

Best regards,

The Engineering Team at E&S Grounding Solutions


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