10-gauge for a 15-amp table saw at 100 feet.

No question. Use a 10-gauge cord. A 12-gauge cord might technically handle 15 amps, but at 100 feet the voltage drop will cause your saw to run sluggish, overheat the motor, and trip breakers more often. You want full power to the blade, not a dimmed-down version.

This is one of those situations where the extra money is worth it. A 10-gauge cord is heavier and less flexible, but it keeps voltage loss under 3% at full load. Your table saw’s motor will thank you, and you won’t have to babysit the breaker.

Don’t even think about 14-gauge — that’s a fire and frustration starter. Go 10-gauge, move on with your project.