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Wire size for 20 amps at 100 feet

20 A at 100 ft one-way

Voltage	Conductor	Minimum size	Voltage drop
120 V	Copper	8 AWG	3.06 V (2.55%)
120 V	Aluminum	6 AWG	3.23 V (2.69%)
240 V	Copper	10 AWG	4.84 V (2.02%)
240 V	Aluminum	8 AWG	5.04 V (2.10%)

Smallest size meeting NEC 75 °C ampacity (with 240.4(D) limits) and ≤3% drop at the full 20 A. Use 125% sizing for continuous loads; apply derating for more than 3 current-carrying conductors or high ambient temperature.

Adjust the numbers

Load current (amps)

One-way length (feet)

Voltage

Conductor

Max voltage drop (%)

Continuous load?

FAQ

What size wire for 20 amps at 100 feet?

At 240 V: 10 AWG copper keeps voltage drop under 3%. See the table for 120 V and aluminum.

Same current, other distances

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