What Gauge Extension Cord Do You Need for Outdoor Power Tools?

Corded electric mowers, pressure washers, chainsaws, and shop vacs have gotten genuinely capable over the last few years, but all of them run into the same overlooked bottleneck: the extension cord between the tool and the outlet. A cord that's too thin or too long for the job doesn't just feel weak — it runs hot, drops voltage, and can shorten the life of the tool's motor.

There's no single 'best' extension cord, because the right gauge depends on two things: how many amps the tool draws and how far the cord has to run. Here's how to work out both numbers and pick a cord that won't bottleneck a tool you've already bought.

Why gauge and length work against each other

Extension cords are sized by gauge, measured in AWG (American Wire Gauge) — and the scale runs backward from what feels intuitive: a lower AWG number means a thicker wire, and thicker wire carries current with less resistance. A 12 AWG cord is physically thicker and safely carries more amps than a 16 AWG cord, even though 12 is the smaller number.

Length matters because electrical resistance builds up over distance. A cord that comfortably powers a tool at 25 feet can cause a meaningful voltage drop at 100 feet, which shows up as a motor that runs weaker, hotter, or hesitates to start under load — exactly the kind of strain that shortens a motor's life over repeated use.

Start with your tool's amp draw, not its price or size

Every corded tool has a nameplate rating, usually stamped near the plug or printed in the manual, listing the amps it draws (sometimes alongside volts and watts). That amp figure — not how big or expensive the tool looks — is what determines the gauge you actually need.

This matters most for tools with a real startup surge. Corded electric pressure washers and corded mowers both pull noticeably more current for a moment when the motor kicks on than they do once running steadily, which is why it's worth sizing a cord generously rather than to the bare minimum. If you're still weighing a corded electric model against gas or battery, our electric vs. gas pressure washer guide and best lawn mowers for small yards roundup both cover where corded tools fit in.

Extension cord gauge chart by length and amp draw

As a practical rule of thumb for 120-volt tools: up to 25 feet, 16 AWG covers tools drawing up to about 13 amps, and 14 AWG covers up to 15 amps. From 25 to 50 feet, step up to 14 AWG for most tools and 12 AWG once you're in the 15-20 amp range. From 50 to 100 feet, 12 AWG is the safer default, moving to 10 AWG for higher-draw tools like pressure washers.

Beyond 100 feet, voltage drop becomes hard to avoid even with a heavy 10 AWG cord — it's worth looking for a closer outlet or a dedicated outdoor circuit instead of relying on an extremely long cord. When a tool's amp draw sits right between two rows on a manufacturer's chart, round up to the thicker gauge rather than down; an oversized cord costs a little more but never hurts the tool.

Match the cord type to outdoor and wet conditions

Gauge isn't the only spec that matters outdoors. Look for a cord jacket rated for outdoor use (often marked with a 'W' in the cord's printed designation, alongside a type like SJTW), since indoor-only cords use a thinner, less weather-resistant insulation that can crack or degrade with sun and moisture exposure.

A three-prong, grounded cord is non-negotiable for any tool with a metal housing or motor, and plugging into a GFCI-protected outlet is especially important for anything used near water — a pressure washer being the obvious example, since you're actively spraying water around the cord and connection point for the entire job.

Common mistakes that strain a cord or a tool

Daisy-chaining two or three shorter cords together to reach farther is one of the most common mistakes — each connection point adds resistance, and the combined length often ends up thinner-equivalent than what the tool actually needs, even if each individual cord was rated fine on its own. Use a single cord of the correct length and gauge instead.

Running a cord while it's still tightly coiled is another one worth avoiding: a coiled cord under load traps heat inside the loops, and over time that heat buildup degrades the insulation faster than if the cord were laid out straight. Leaving cords outside permanently, uncoiled in dirt or standing water, shortens their life the same way weather eventually shortens a hose's.

Quick picks by tool type

Corded electric mowers typically draw 10-12 amps — a 14 AWG cord handles most yards up to 50 feet, and 12 AWG is the safer call beyond that.

Corded electric pressure washers often draw 12-15 amps with a startup surge above that — 12 AWG is a reasonable default past 25 feet, and worth checking against the washer's own manual, since pressure washer motors are usually the highest-draw corded tool most homeowners own.

Corded electric chainsaws draw around 12 amps for most homeowner models — the same 14-to-12 AWG guidance as a corded mower applies. Our battery vs. gas chainsaw guide covers where a corded saw fits in next to those two options if you're still choosing a power source.

Shop vacs vary more by motor size, but most draw 6-10 amps — on the lighter end of this list, so a 16 or 14 AWG cord is usually fine unless you're running a long distance across a garage or job site.