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Wire size for 125 amps at 100 feet

125 A at 100 ft one-way

Voltage	Conductor	Minimum size	Voltage drop
120 V	Copper	1/0 AWG	3.05 V (2.54%)
120 V	Aluminum	3/0 AWG	3.15 V (2.62%)
240 V	Copper	1 AWG	3.85 V (1.60%)
240 V	Aluminum	2/0 AWG	3.98 V (1.66%)

Smallest size meeting NEC 75 °C ampacity (with 240.4(D) limits) and ≤3% drop at the full 125 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 125 amps at 100 feet?

At 240 V: 1 AWG copper keeps voltage drop under 3%. See the table for 120 V and aluminum.

Same current, other distances

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