Copper Resistance vs Temperature Calculator (Winding and Wire Temperature)

Resistance of a copper conductor at another temperature, or the temperature from a resistance change.

Inputs

Calculate Resistance at the reference temperature (Ω) Reference temperature (°C) New temperature (°C) Measured resistance now (Ω) Temperature coefficient α

Results

R2 = R1 · (1 + α · (T2 − T1)) with α = 0.00393 /°C for copper at 20 °C (annealed copper; equivalently T2 = (R2/R1)·(234.5 + T1) − 234.5). The temperature found this way is the average over the whole conductor.

For preliminary assessment only — the final decision must follow the manufacturer’s datasheet and the applicable NEC / IEC / UL standards. Results are calculated from the standard formulas stated on this page and are for design estimates only. They are not a rating of any specific part — always confirm current, voltage, temperature and environment limits against the manufacturer’s datasheet for the part you intend to use.

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