Extension cord gauge chart
A 15 amp tool on a 25 ft extension cord needs 14 AWG, and on 100 ft it needs 12 AWG. A 10 amp load needs 16 AWG at 50 ft. The chart keeps the voltage drop at 120 V within 5%.
| Load | 25 ft | 50 ft | 100 ft | 150 ft |
|---|---|---|---|---|
| 5 A (600 W) | 18 AWG | 18 AWG | 16 AWG | 14 AWG |
| 8 A (960 W) | 18 AWG | 16 AWG | 14 AWG | 12 AWG |
| 10 A (1,200 W) | 18 AWG | 16 AWG | 12 AWG | 12 AWG |
| 13 A (1,560 W) | 16 AWG | 14 AWG | 12 AWG | 10 AWG |
| 15 A (1,800 W) | 14 AWG | 14 AWG | 12 AWG | 10 AWG |
Extension cord ratings by gauge
| Cord gauge | Rating, amps |
|---|---|
| 18 AWG | 10 A |
| 16 AWG | 13 A |
| 14 AWG | 18 A |
| 12 AWG | 25 A |
| 10 AWG | 30 A |
Ratings are for a cord with two current-carrying conductors, like a standard three-prong extension cord. A household plug and outlet are rated 15 A, so a cord rated higher still carries no more than 15 A through a standard plug.
How the cord gauge is chosen
Each cell is the thinnest cord rated for the load whose voltage drop at 120 V stays within 5%. A dash means no common cord gauge is enough: move the tool closer to the outlet or use a shorter, heavier cord. The amp rating on the tool's nameplate is the load to look up.