Longer runs need thicker wire — here’s the rule of thumb

Yes, length matters — a lot.

Every foot of extension cord adds resistance, which means voltage drop and heat. The longer the cord, the less current you can safely draw at the same wire gauge.

For 120V tools, the practical rule of thumb is to keep voltage drop under 3% (about 3.6V). Here’s what that looks like with common gauges:

• 50 feet: 14-gauge is fine for up to 15 amps. You won’t notice a drop.
• 100 feet: You want 12-gauge for 15 amps. 14-gauge will drop close to 4% at full load — your saw will run slower, the motor will get hotter.
• 150 feet: Step up to 10-gauge. Even 12-gauge drops almost 6% at 15 amps — that’s noticeable. Lights dim, tools struggle.

If you’re pulling 20 amps, double those gauges (12 at 50ft, 10 at 100ft, 8 at 150ft).

Also, don’t coil a long cord under load. The heat can’t escape and you melt the insulation. Future You will not enjoy that.

Buy the right gauge for the length you actually need. It’s not where you save eight bucks.