12-gauge extension cords are for real work.

Short answer: 12-gauge handles 20 amps, 14-gauge handles 15 amps. That difference matters when you’re running a circular saw or a space heater.

14-gauge is fine for lights, fans, phone chargers, and most household stuff that draws under 15 amps. It’s cheaper, lighter, and easier to coil. But plug a table saw into a 14-gauge cord and you might trip a breaker or start a fire if the cord is long. Voltage drop is real.

12-gauge is the default for power tools, shop vacs, air compressors, and anything that makes noise. It handles 20 amps, so it’s safer when the tool pulls a lot of juice at startup. I only buy 12-gauge cords for the garage. The extra weight is worth not worrying.

One more thing: If you’re running a cord more than 50 feet, bump up to 10-gauge. Long distance kills ampacity faster than you think.