Voltage Drop Table

Voltage drop on a lighting circuit depends on the wire gauge, the run length, and the current. This table gives the DC resistance of common copper and aluminum conductors, the basis for any voltage-drop calculation.

Wire (AWG) Copper (ohm/1000 ft) Aluminum (ohm/1000 ft)
14 3.07 —
12 1.93 3.18
10 1.21 2.00
8 0.764 1.26
6 0.491 0.808
4 0.308 0.508
2 0.194 0.319
The drop formula. For a single-phase run: voltage drop = 2 × (resistance per 1000 ft ÷ 1000) × length × current. Keep branch-circuit drop under about 3%.

See the Voltage Drop Calculator and the Voltage Drop Formula.

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The calculators and tools on Formula Factory are provided for general guidance and informational purposes only. Results are estimates based on standard formulas and the values you enter — they do not constitute professional engineering, electrical, or architectural advice. Always verify calculations with a qualified professional before making decisions for any safety-critical, code-compliance, or commercial application. Formula Factory makes no representations or warranties as to the accuracy or completeness of any result, and accepts no liability for errors, omissions, or any outcomes arising from reliance on this information.