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Extension Cord Gauge Chart by Length and Amperage
Longer cords and higher-draw tools both need thicker wire (a lower gauge number) to avoid dangerous voltage drop and heat buildup. Using an undersized cord for the length and load is a common cause of underpowered tools and, in worse cases, a fire hazard.
| Cord length | Up to 7 amps (drills, small tools) | 7-10 amps (mid tools) | 10-15 amps (saws, heaters) |
|---|---|---|---|
| 25 ft | 16 AWG | 14 AWG | 14 AWG |
| 50 ft | 16 AWG | 14 AWG | 12 AWG |
| 100 ft | 14 AWG | 12 AWG | 10 AWG |
| 150 ft | 12 AWG | 10 AWG | 10 AWG or avoid |
Notes
- Lower gauge numbers mean thicker wire and higher current capacity — a 12 AWG cord carries more current safely than a 16 AWG cord of the same length.
- Coiled cords heat up faster than fully uncoiled ones; always uncoil a cord fully when running power tools for extended periods.
- Outdoor extension cords must be rated for outdoor use (marked 'W' or 'WA'), which adds weatherproof insulation beyond what indoor-rated cords have.
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