How Long Can an Extension Cord Be?
There is no single length limit — a cord's safe length depends on its gauge AND what's plugged into it. A 12 AWG cord safely handles a 20A tool through about 50ft, but by 100ft its safe rating drops to roughly 11A per our Cord Gauge Ampacity Index. The thinner the gauge or the heavier the load, the shorter the safe run.
Voltage drop is why length matters
Every foot of cord adds resistance, and more resistance means more voltage lost before it reaches the tool or appliance. Past a certain length for a given gauge and amperage, that voltage drop exceeds the commonly-cited 3% safe limit for branch circuits — motors run hotter and weaker, lights dim, and heating elements underperform. Full explainer: What Does Voltage Drop Mean for Extension Cords?
Daisy-chaining cords does not help
Connecting two cords end to end uses the same voltage-drop math as one cord of the combined length — and the chain is only ever as capable as its thinnest section. If you need more reach, buy one cord in the correct gauge for the full distance, not a chain of shorter cords.
This page is general reference, not an electrical code determination.
Frequently Asked Questions
There's no single length limit — it depends on the gauge and the load. A thin 18 AWG cord is only safe for a light load past about 50ft; a 12 AWG cord holds up to a 20A tool through 50ft but drops to roughly 11A by 100ft. See the Cord Gauge Ampacity Index for the exact length-by-gauge-by-amperage breakdown.
Voltage drop. As a cord gets longer, its resistance increases, so more of the circuit's voltage is lost before it reaches the tool or appliance. Past a certain length for a given gauge and load, the voltage drop exceeds the commonly-cited 3% safe limit — undervolting motors, dimming lights, and causing overheating in some equipment.
Practically, yes — most manufacturers don't recommend daisy-chaining more than roughly 100ft of standard-gauge cord for anything beyond light loads, and very long runs (150ft+) generally require stepping up to a heavier gauge (10, 8, or 6 AWG) to keep voltage drop in check for real tools or appliances.
You can, but the combined length uses the SAME voltage-drop math as a single cord of that total length — daisy-chaining doesn't improve anything, and connecting a thin cord to a thick one means the whole chain is only as capable as its thinnest, weakest section.