Wire Resistance Calculator by AWG

Resistance grows with length and shrinks with conductor area.

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Formula

R = K × L ÷ CM

Example calculation

100 ft of 12 AWG copper ≈ 0.198 Ω.

Practical HVAC use

Estimate losses or check thermostat/low-voltage runs.

Common mistakes

Forgetting a circuit has two conductors.

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Educational tool. Results are estimates from the stated formulas; always confirm with manufacturer data and the code adopted in your jurisdiction. All calculators