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A cordless impact wrench delivers the torque you need for lug nuts, lag bolts, deck screws into ledger boards, and structural bolting. These tools hit harder than cordless ratchets and drills. The 1/2-inch anvil models covered here put out 700 to 1,400 ft-lbs of breakaway torque. This guide covers specs, brand options, and what to look for before you buy.
An impact wrench uses a hammer-and-anvil mechanism to deliver high rotational torque in short bursts. The motor spins a weighted hammer that strikes an anvil connected to the output shaft. Each strike transfers energy to the fastener without transferring reaction torque back to your wrist. That is why you can remove a 150 ft-lb lug nut one-handed with an impact wrench but need a breaker bar and body weight with a regular socket wrench.
Cordless impact wrenches run on 18V or 20V lithium-ion batteries and deliver 700 to 1,400 ft-lbs of breakaway torque depending on the model. Most have a 1/2-inch anvil (the square drive that accepts sockets), though 3/4-inch models exist for heavy equipment. Key specs are max torque, breakaway torque (the initial force to loosen a stuck fastener, which is always higher than sustained torque), impacts per minute (IPM), RPM, and weight.
Common applications: automotive lug nuts (80-120 ft-lbs), lag bolts into framing lumber (150-200 ft-lbs), deck ledger board connections (250+ ft-lbs), and structural bolting. If you are doing tire rotations, suspension work, or framing with lag bolts, an impact wrench saves significant time over hand tools.
We break down specs, prices, and trade-offs in our best impact wrenches guide.
The sustained fastening torque the wrench delivers. Entry-level models produce 300-450 ft-lbs. Mid-range hits 500-750 ft-lbs. Professional models reach 1,000+ ft-lbs. Lug nuts on passenger vehicles need 80-120 ft-lbs. Lag bolts into framing need 150-250 ft-lbs. Structural bolting on steel can require 500+ ft-lbs. Buy for your heaviest regular use case, not your lightest.
The peak torque on the first few impacts when loosening a stuck fastener. Always higher than max torque because the hammer mechanism delivers more energy in short bursts against resistance. A wrench rated at 700 ft-lbs max might hit 1,200 ft-lbs breakaway. This spec matters most for corroded lug nuts, old lag bolts, and anything that has been sitting for years.
The square drive that accepts sockets. 1/2-inch is the standard for automotive and construction work. It fits standard impact sockets from 3/8-inch to 1-1/2-inch hex sizes. 3/4-inch anvils exist for heavy equipment, crane assembly, and industrial bolting. For home and professional automotive use, 1/2-inch covers everything you will encounter.
How fast the output shaft spins. Higher RPM runs down loose fasteners faster. Most models offer 0-1,750 to 0-2,400 RPM with a variable-speed trigger. Some have 2 or 3 speed settings so you can reduce output for smaller fasteners. RPM matters less than torque and IPM for break-loose work, but it speeds up repetitive tasks like running down a row of lag bolts.
How many hammer strikes the mechanism delivers per minute. Typical range is 1,800 to 3,200 IPM. Higher IPM means the wrench hits the fastener more frequently, which can break stubborn bolts free faster. The relationship between IPM and torque is not linear. A model with lower IPM but higher torque per impact can outperform a high-IPM low-torque model on stuck fasteners.
Bare tool weight runs 4 to 8 lbs. Add 1-2 lbs for the battery. If you do overhead work, under-vehicle work, or hold the wrench for extended periods, lighter matters. The Bosch GDS18V-740 is the lightest in this group at 4.6 lbs. The Milwaukee 2767-20 is the heaviest at about 6.8 lbs. That 2.2 lb difference is noticeable after 30 minutes of tire rotations.
A 1/2-inch anvil handles lug nuts, lag bolts, deck fasteners, and nearly all automotive and residential construction fasteners. A 3/4-inch anvil is for heavy equipment, crane assembly, and industrial bolting where fasteners exceed 1-1/2-inch hex. If you are doing home, auto, or general construction work, 1/2-inch is the correct choice. You would know if you needed 3/4-inch because the fasteners would be too large for a 1/2-inch socket set.
Passenger car lug nuts are torqued to 80-100 ft-lbs from the factory. Light truck lug nuts run 100-140 ft-lbs. With corrosion and thread-locking compounds, the breakaway torque to loosen them can reach 200-300 ft-lbs. A budget impact wrench with 300 ft-lbs handles most passenger vehicles. For trucks and SUVs, aim for 500+ ft-lbs to have headroom for stubborn fasteners. The Milwaukee 2767-20 at 1,400 ft-lbs breakaway handles anything you will encounter on the road.
Pneumatic impact wrenches need an air compressor, hose, and fittings. They are lighter (3-4 lbs), deliver consistent power, and cost less upfront ($40-$150). The compressor is the expensive part ($200-$800). Cordless impact wrenches go anywhere, start instantly, and the top models now match pneumatic torque output. The trade-off: batteries add weight and need charging. For a fixed shop with compressed air already plumbed, pneumatic is still the cost-effective choice. For mobile work, job sites, or home garages without a compressor, cordless is the clear winner.
No. Use impact-rated sockets only. Regular chrome sockets are hardened and brittle. The repeated hammering from an impact wrench can shatter them, sending metal fragments at high speed. Impact sockets are made from softer chrome-molybdenum steel that absorbs the impact energy without cracking. They are thicker-walled and usually black oxide coated. A 1/2-inch impact socket set runs $30-$80. Do not skip this.
Three-speed settings are useful. Low speed (around 1,200 RPM) prevents over-tightening on small fasteners like brake caliper bolts. Medium speed handles general fastening. High speed (2,400 RPM) runs down lag bolts and removes lug nuts quickly. Single-speed models work fine if you develop trigger control, but beginners benefit from the guardrails. Most models in the $150+ range include at least two speed settings.
A 5.0Ah battery gets 150-250 lug nut removals on a full charge, roughly 1-2 hours of intermittent use. Heavily corroded fasteners drain it faster. A 9.0Ah battery extends that to 300-500 removals. For a weekend tire rotation (20 lug nuts), a single 5.0Ah charge is more than enough. For all-day shop or job site use, carry two batteries and a charger. Charge time runs 45-90 minutes depending on the battery and charger model.