What Is an Impact Driver?

It looks like a stubby drill, but it works very differently. Here is what an impact driver does, how it does it, and whether you need one.

Updated October 10, 20266 min readBy the ImpactDriver.net team

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What an impact driver is

An impact driver is a cordless (occasionally corded) tool designed for one job: turning fasteners. Unlike a drill, which delivers smooth, continuous rotation, an impact driver adds a rotational hammering action when the fastener pushes back. Each blow nudges the screw a little further, so the tool keeps advancing where a drill would stall.

You can recognize one by three features:

• A short, compact head. Most current 18V and 20V models measure about 4 to 5.5 inches from the back of the motor to the tip of the collet.
• A 1/4-inch hex collet instead of a three-jaw chuck. You pull back a sleeve (or simply push the bit in, on newer one-handed designs) and the bit locks in place.
• A rapid, rattling sound under load. That is the hammer mechanism at work, and it is the giveaway that you are holding an impact driver, not a drill.

How an impact driver works

The mechanism is simple once you see it in order:

1. The motor spins a gearbox, which turns a heavy metal piece called the hammer.
2. The hammer drives the anvil, the part attached to the bit holder. With little resistance, hammer and anvil turn together and the tool behaves like a fast screwdriver.
3. When the screw resists, the hammer slides backward against a spring, slips past the anvil's lugs, and snaps forward again to strike them.
4. That cycle repeats thousands of times per minute. Spec sheets list it as IPM (impacts per minute) or BPM (blows per minute). Current 18V models are rated roughly 3,600 to 4,400 IPM.

Because the force arrives in short, sharp bursts instead of one continuous twist, much less of it travels back into your wrist. This is why an impact driver can sink a 6-inch structural screw while you hold it with one hand, while a drill doing the same job would try to wrench itself out of your grip. For a deeper look, see how an impact driver works.

What impact drivers are best at

An impact driver shines whenever there are a lot of fasteners or long ones:

• Deck boards and framing with 2.5 to 3.5-inch screws
• Structural screws and lag bolts (with a hex-to-socket adapter)
• Ledger boards, fence rails, pergolas and sheds
• Self-tapping screws into steel studs and sheet metal
• Cabinet installation and long screws through face frames
• Driving Tapcon concrete screws after the hole is drilled
• Breaking loose stubborn screws and small bolts

See the full list of what an impact driver is used for, with the bit and setting for each job.

What impact drivers are not good at

• Drilling masonry. The hammering is rotational, not forward, so it does almost nothing against concrete. You need a hammer drill or rotary hammer.
• Precision drilling. The hex collet allows some wobble, and drill bits must have hex shanks.
• Delicate fasteners. Most impact drivers have no clutch. Small brass screws, hinge screws and particleboard furniture are easy to overdrive or snap. Use the lowest setting or a drill with a clutch.
• Large hole saws and big auger bits in hardwood. They grab, chatter and overheat the tool. A drill does this better.
• Lug nuts and suspension bolts. Some models can break loose a lug nut, but this is impact wrench work.

Impact driver vs drill at a glance

Torque ratings are measured differently by each brand, so compare them within a brand rather than across brands. The full breakdown is in impact driver vs drill.

Key specs, decoded

Torque (in-lbs)

The peak twisting force, in inch-pounds. Twelve in-lbs equal one ft-lb, so a 2,000 in-lb impact driver is rated at about 167 ft-lbs. That sounds like a lot, but it is a peak figure from a short impact. Real driving performance depends just as much on speed and blow rate. More detail in impact driver torque explained.

RPM and IPM

RPM is how fast the bit spins with no load. IPM is how many blows it delivers per minute once impacting. Higher numbers usually mean faster driving of long screws. See IPM vs RPM.

Speed settings and modes

Most current models have three or four speed settings. Many add special modes, such as a self-tapping screw mode that slows down once the screw pierces metal, or an assist mode that starts slowly and then speeds up. These modes are the closest thing an impact driver has to a clutch. See speed settings and modes.

Brushless motor

Brushless motors run cooler, last longer and get more work from each battery charge. Almost every model worth buying in 2026 is brushless. See brushless vs brushed.

Cordless, 12V or 18V?

Nearly all impact drivers sold today are cordless. The choice is mostly between two classes:

• 12V (Milwaukee M12, DeWalt 12V MAX, Makita CXT, Bosch 12V): lighter and smaller, ideal for electricians, HVAC techs, cabinet installers and most indoor home jobs. Milwaukee's M12 FUEL is rated at 1,500 in-lbs.
• 18V / 20V MAX (Milwaukee M18, DeWalt 20V MAX, Makita LXT, Ryobi ONE+): the default for decks, framing and heavy fasteners. Flagships are rated around 1,800 to 2,200 in-lbs.

"20V MAX" and "18V" are the same battery class, labeled differently (why the numbers differ). If you already own batteries from a brand, stay with it. A bare tool costs far less than starting a new platform. Compare classes in 12V vs 18V.

What else you need

• Impact-rated bits. A few Phillips #2, square #2 and Torx T25 bits cover most screws. Ordinary bits snap quickly under impact. See impact driver bits.
• A magnetic bit holder or 2-inch power bits for reach and better screw retention.
• Hearing and eye protection. The hammer mechanism is loud, and snapped bits can fly.
• Optional: a hex-to-1/4 or 3/8-inch square adapter for sockets, and hex-shank drill bits for pilot holes.

Impact-rated bit sets on Amazon Our bit set picks

Do you need one?

If you drive more than a handful of screws longer than 2 inches each year, such as for a deck, a fence, a shed, cabinets or a garage shelving build, an impact driver will save time and wrist strain. If your work is mostly hanging pictures, assembling flat-pack furniture and drilling the occasional hole, a good drill/driver alone is enough. Work through the decision guide if you are on the fence.

The best value for most first-time buyers is a drill and impact driver combo kit, which usually costs little more than the drill alone plus batteries. To compare individual models, start with the best impact drivers of 2026. To learn the technique, read how to use an impact driver.

Frequently asked questions