1/2 vs 3/8 Impact Wrench: Which One Should You Buy?

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1/2 vs 3/8 impact wrench: the short answer

Buy 1/2 in for wheels, suspension and anything rusted: the DEWALT DCF891B states 600 ft-lbs fastening and 800 ft-lbs breakaway with 4 speed settings and a 3 year warranty. Buy 3/8 in for engine bays and tight fasteners: the Astro 1828 states 500 ft-lbs in a 3.85 in body, the DEWALT DCF913B states 250 ft-lbs tightening in a 5.87 in cordless body, and the Ingersoll Rand 15QMAX states up to 475 ft-lbs in a 4.6 in body. Two of the four are cordless 20V, two are pneumatic, so the air supply question matters as much as the drive size. For the next size up, see our corded vs cordless impact wrench comparison.

Torque: what each listing states

Wrench	Drive	Stated torque	Length	Weight	Power
DEWALT DCF891B	1/2 in	600 / 800 ft-lbs	8.88 in	4.3 lb	20V cordless
Astro 1828	3/8 in	500 ft-lbs	3.85 in	3.53 lb	Pneumatic
DEWALT DCF913B	3/8 in	250 / 400 ft-lbs	5.87 in	2.3 lb	20V cordless
Ingersoll Rand 15QMAX	3/8 in	475 ft-lbs	4.6 in	2.4 lb	Pneumatic

The 1/2 in DEWALT leads on stated torque by a wide margin: 600 ft-lbs fastening and 800 ft-lbs breakaway, with 4 speed settings, a variable speed trigger and precision wrench control to avoid overtightening. Among the 3/8 in picks, the Astro states the highest figure at 500 ft-lbs with a twin hammer design, followed by the Ingersoll Rand at a stated 475 ft-lbs and the DEWALT DCF913B at 250 ft-lbs tightening and 400 ft-lbs breakaway. Note the listing conflicts below before comparing these numbers: two listings state two different torque figures in different fields.

Drive size and access

Drive size sets the socket system and, roughly, the tool’s size. The 3/8 in guns are the compact ones: the Astro at 3.85 in long, the Ingersoll Rand at 4.6 in and the DEWALT DCF913B at 5.87 in, weighing 2.3 to 3.53 lb. The 1/2 in DEWALT is 8.88 in and 4.3 lb, a bigger tool for bigger fasteners. The Astro’s sub-4-inch length is the stated access champion here; the 1/2 in gun will not follow it into tight spots. Match the drive to the fasteners you touch most: 3/8 in sockets for engine work, 1/2 in for wheels and chassis.

Cordless vs air

Two listings are 20V cordless (both DEWALTs, both bare tool only, so the battery is a separate purchase) and two are pneumatic (Astro and Ingersoll Rand). The Astro states 4.8 CFM air consumption with Hi-Flo fittings suggested; the Ingersoll Rand states no CFM figure. Cordless means no hose and no compressor, at the cost of battery weight: the 1/2 in DEWALT is 4.3 lb before the battery. Pneumatic means lighter guns, 2.4 and 3.53 lb, but a compressor that can feed them. Our corded vs cordless impact wrench guide covers the power question in more depth.

Where the listings disagree with themselves

Impact wrench listings contradict themselves, and the conflicts sit in the torque fields:

• Astro 1828: the bullets state 500 ft-lbs max torque while the spec table lists max torque as 450 ft-lbs and item torque as 500 ft-lbs. The bullets also state 3.53 lb while the spec table states 3 lb.
• Ingersoll Rand 15QMAX: the title states up to 475 ft-lbs while the spec table lists max torque reverse output and item torque as 380 ft-lbs.

When the bullets and the spec table disagree, plan around the lower figure when it matters.

What this guide does not cover

This guide covers impact wrench hardware only. It does not cover sockets, adapters, air compressors or torque specifications for specific vehicles. Check your vehicle’s manual for fastener torque specs.

More buying advice: matching the gun to the job

Speed settings against a single speed

The DEWALT DCF891B states 4 speed settings with a variable speed trigger and precision wrench control to avoid overtightening. The other three listings state no speed settings. Speed control matters when the same gun runs lug nuts down and then snugs small bolts: full power on a small fastener snaps it. If the gun will touch fasteners of very different sizes, the DEWALT’s stated settings are a real advantage; if it only breaks loose big nuts, one speed is enough.

Bare tool math

Both DEWALTs are bare tool only: the battery is a separate purchase. The pneumatic guns need no battery but need a compressor. Add the battery cost to the cordless guns and the compressor cost to the air guns before comparing prices: the cheapest gun on the page is not always the cheapest setup in the garage. The Astro’s stated 4.8 CFM consumption sets the compressor bar; a small pancake compressor may not keep up.

Frequently Asked Questions

Which drive size should I buy for lug nuts?

The 1/2 in DEWALT DCF891B: it states 600 ft-lbs of fastening torque and 800 ft-lbs of breakaway torque, the highest stated figures here, with 4 speed settings.

Which of these is the most compact?

The Astro 1828 at 3.85 in long, a 3/8 in pneumatic gun. The Ingersoll Rand follows at 4.6 in and the DEWALT DCF913B at 5.87 in.

Do the pneumatic models need a compressor?

Both list pneumatic operation. The Astro states 4.8 CFM consumption with Hi-Flo fittings suggested; the Ingersoll Rand states no CFM figure, so check your air supply against the tool.

Which of these state a warranty?

Both DEWALTs state a 3 year warranty on material and workmanship. The Astro states a 1 year warranty and the Ingersoll Rand a 2-year warranty.

Can a 3/8 in impact wrench replace a 1/2 in?

Not on stated torque: the 3/8 in picks state 250 to 500 ft-lbs against the 1/2 in gun’s 600 ft-lbs fastening and 800 ft-lbs breakaway. The 3/8 in guns win on access and weight instead.

Related: our compact vs mid torque impact wrench, best 3/8 cordless impact wrench and best air impact wrench for home garage guides.