Electrical
Cable Resistance Calculator
Calculate temperature-adjusted conductor resistance or solve metal area and length. Compare SI/US results and review the method, assumptions and related references below.
Change any input to update the calculation. Unit changes preserve the physical quantity.
Inputs
Calculated locally in your browser. No sign-up or input upload.
Results
Total path resistance
0.4138 ΩOne conductor resistance
0.2069 ΩCalculated metal area
2.5 mm²0.0039 in²One-way length
30 m98.4252 ftTotal conductor length
60 m196.8504 ftResistance per conductor km
6.8964 Ω/kmCalculation breakdown
- Result interpretation
- Calculate temperature-adjusted conductor resistance or solve metal area and length
Assumptions & checks
Ideal DC metal resistance; joints, stranding tolerances, skin/proximity effects and reactance excluded. Solved metal area is not an approved wire size or ampacity.
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Where does this result go next?
Formula
Calculate temperature-adjusted conductor resistance or solve metal area and length
Worked example
Using the default values shown in the calculator, the same formula gives the following result. This is a quick sanity check for the calculation, not a design recommendation.
Inputs
- Conductor material
- Copper
- Resistance path
- Outgoing + identical return
- Conductor temperature
- 20 °C
- Metal cross-sectional area
- 2.5 mm²
- One-way conductor length
- 30 m
Result
- Total path resistance
- 0.4138 Ω
- One conductor resistance
- 0.2069 Ω
- Calculated metal area
- 2.5 mm²
- One-way length
- 30 m
- Total conductor length
- 60 m
- Resistance per conductor km
- 6.8964 Ω/km
Technical references for this calculation
Frequently asked questions
What does this result tell me?
Ideal DC metal resistance; joints, stranding tolerances, skin/proximity effects and reactance excluded. Solved metal area is not an approved wire size or ampacity.
How can I check the calculation?
Worked example: Copper, 2.5 mm², 30 m one way, 20°C, identical return: loop resistance 0.413784 Ω. Review each stated input and unit; use project-specific values rather than treating the editable example as a requirement.
Reference data & method sources
- NIST SI conversion factors
SI/US dimensional conversions. Geometry and energy balances are stated explicitly, not attributed to a design standard.
- US Bureau of Standards Copper Wire Tables
Bulk copper resistance at 20°C; authored temperature/length/area model.
- US Bureau of Standards Aluminum Wire Tables
Bulk aluminum resistance at 20°C. Actual product conductors can differ.