Welder (240V)
What size extension cord for a Welder (240V)?
A welder (240v) draws about 40 amps (9600W) at 240V. To carry that safely you need at least 8 AWG copper, and even then only for short runs, up to roughly 25 ft before voltage drop and heat become a problem. Thinner cord (the common 16 AWG household type) can overheat under this load and is a fire risk.
Cord gauge by length for a welder (240v)
The longer the cord, the thicker it must be to keep voltage drop under 3% at 40A. Minimum recommended copper gauge by run length:
| Cord length | Minimum gauge | Notes |
|---|---|---|
| 25 ft | 8 AWG | Minimum safe gauge |
| 50 ft | 8 AWG | Minimum safe gauge |
| 100 ft | 8 AWG | Minimum safe gauge |
| 150 ft | 6 AWG | Upsized for the longer run |
Safety note
240V welders need a special heavy-duty extension cord, 8 AWG minimum with appropriate NEMA 6-50 or 14-50 plugs.
Why gauge matters
A smaller AWG number means thicker copper and lower resistance. Undersized cord drops voltage (making motors and heating elements work harder) and turns the lost energy into heat in the cord itself. At 40A, a too-thin or coiled cord can get hot enough to melt insulation. Always uncoil cords fully during use, and never chain two cords together for a high-draw welder (240v).
Frequently asked questions
What gauge extension cord for a welder (240v)?
Use at least 8 AWG copper for a welder (240v) (40A). For runs longer than 25 ft, step up to the next thicker gauge to hold voltage drop under 3%.
How long can the extension cord be?
At 8 AWG, keep it to about 25 ft for a welder (240v). Beyond that, use a thicker cord: see the gauge-by-length table above.
Can I use a regular 16 AWG cord?
No. A standard 16 AWG household cord is not rated for the 40A a welder (240v) draws and can overheat. Use 8 AWG or thicker, and ideally plug the welder (240v) directly into a wall outlet.
Disclaimer: For reference only. Consult a licensed professional.