Wire size for 40 amps at 100 feet

40 A at 100 ft one-way

Smallest size meeting NEC 75 °C ampacity (with 240.4(D) limits) and ≤3% drop at the full 40 A. Use 125% sizing for continuous loads; apply derating for more than 3 current-carrying conductors or high ambient temperature.

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FAQ

Same current, other distances

• 40 A at 25 ft
• 40 A at 50 ft
• 40 A at 75 ft
• 40 A at 125 ft
• 40 A at 150 ft
• 40 A at 200 ft
• 40 A at 250 ft
• 40 A at 300 ft
• 40 amp wire size chart