100 feet is fine for a 12-gauge cord on a 15-amp miter saw.

Breaker tripping isn’t the issue here—it’s voltage drop. A 12-gauge cord can handle 15 amps at 100 feet without enough voltage loss to hurt your saw or trip anything. Go longer than that and you might starve the motor, making it sluggish or overheating it over time.

100 feet is a common recommendation. If you need more, step up to 10-gauge. But for almost every job site, 50–100 feet of 12-gauge works perfectly. Don’t overthink it.

The breaker doesn’t care about cord length—it cares about a dead short or an overloaded circuit. Your saw won’t overload it if the circuit is properly sized.