12-gauge for a 15-amp tool at 50 feet.

Any smaller and you risk voltage drop, motor damage, or a tripped breaker. 14-gauge might barely work but why gamble? At 50 feet the resistance adds up.

The rule: for 15 amps, use 12-gauge wire if the run is over 25 feet. Under that, 14-gauge is fine. But most shop tools are 15 amps, and 50 feet is common. Just buy the 12-gauge cord and be done.

A too-thin cord makes the motor run hot. It’ll still spin, but it’s pulling extra current to compensate. That burns up tools faster.

Don’t save twelve bucks on an extension cord.