Earthing Conductor Size Calculator
Earthing conductor size from fault current and time.
Runs in your browser. Nothing is uploaded — your input is processed on this device and discarded when you close the tab.
Earthing Conductor Size Calculator
How to use this tool
- Enter the prospective fault current in amps and how long the fault lasts in seconds.
- Enter the k factor for your conductor material and insulation (143 is a common copper value).
- Press Generate to see the minimum cross-section and the next standard size.
Worked example
Fault current 5,000 A for 0.5 s with k = 143: 5,000 x square root of 0.5 / 143 = 24.72 sq mm, so the next standard size is 25 sq mm.
What this tool does not do / Limits
This is a sizing estimate from user-entered values with stated assumptions only, using S = I x square root of t / k. It is explicitly not a substitute for a qualified electrician or local electrical code compliance. Real sizing also depends on the fault loop, protective device, conductor type, temperature and local rules, so have the design checked by a qualified person.
Frequently asked questions
What is the k factor?
A value that reflects conductor material, insulation and temperature limits; it changes the result a lot, so use the value from the applicable standard for your exact conductor.
Why pick the next standard size up?
Conductors are sold in standard sizes, so you round up to the first size that meets or beats the calculated minimum.
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