Wire Resistance Calculator
Estimate one-conductor and single-phase round-trip resistance from material, conductor size, length, and temperature.
Enter conductor and load values
Conductor resistance
About this calculator
Estimate one-conductor and single-phase round-trip resistance from material, conductor size, length, and temperature.
The base table provides listed AC resistance at 75°C. The entered temperature adjustment is a first-order approximation and does not model AC reactance, skin/proximity effects, or connection resistance.
Method and assumptions
One-conductor resistance = temperature-adjusted resistance per 1,000 ft × one-way length ÷ 1,000. Single-phase round-trip resistance is twice the one-conductor value.
Resistance values use the site’s listed 75°C AC conductor data. Temperature adjustment is a first-order estimate; measured or manufacturer values for the installed conductor take precedence.
FAQs
Are listed conductor resistance values exact for an installed circuit?
No. Actual resistance depends on conductor construction, operating temperature, installation, connections, and parallel arrangement. Use project-specific manufacturer or engineering data when available.
Does this verify conductor ampacity or code compliance?
No. These tools estimate resistance, I-squared-R loss, or cumulative voltage drop only. Ampacity, conductor sizing, protection, installation, and local requirements need separate review.
Sources
Conductor resistance data is attributed in the calculation registry to Southwire cable specifications; verify conductor-specific data for the installed cable.