Table of Contents

Cordless Impact Wrench 1/2 Inch, 3/8 or 3/4: Which Size?

Drive size is the first decision in specifying an impact wrench, because it sets the ceiling on torque, the sockets that fit, and the weight the operator carries all day. Get it wrong and no other specification rescues the choice.

The M7 cordless range covers three sizes. A cordless impact wrench in 3/8 in., 1/2 in. or 3/4 in. drive is selected by the fastener, access and torque the work actually requires.

Cordless Impact Wrench Drive Size: What It Actually Decides

The square drive is the male anvil the socket fits onto, and its size governs three things at once: the maximum torque the tool can transmit without damaging the joint between tool and socket, the socket range available to you, and the physical size of the tool.

Those three move together. A larger drive is a larger anvil, a larger hammer mechanism and a heavier housing. You do not buy torque on its own — you buy it along with the bulk that carries it.

Square drive	Max. torque in the M7 cordless range	Tool weight	M7 models
3/8 in. (9.5 mm)	434 Nm / 320 ft-lb	1 kg (bare tool)	DS-204
1/2 in. (12.7 mm)	894–1700 Nm / 660–1250 ft-lb	1.16–3.33 kg	DW-401, DW-404, DW-404K, DW-405, DW-IW400, DW-C401, DW-406, DW-402
3/4 in. (19 mm)	1900 Nm / 1400 ft-lb	3.37 kg	DW-601

3/8 in.: Access Before Power for a Cordless Impact Wrench

A 3/8 in. drive is specified when the tool has to reach the fastener at all, not when it has to be the strongest tool on the bench.

The M7 DS-204 is 115 mm (4-1/2 in.) overall and 1 kg as a bare tool. In an engine bay, behind a dashboard, or inside a machine guard, a shorter tool that fits is worth more than a longer one that does not.

Its published figures set the boundary clearly:

Maximum torque 434 Nm / 320 ft-lb
Torque settings 152 / 195 / 304 / 434 Nm (112 / 144 / 224 / 320 ft-lb)
Bolt capacity M5–M8 screw, 8–13 mm nut

That bolt capacity is the number to read, not the headline torque. A tool rated to an 8–13 mm nut is not the tool for a wheel nut, whatever its peak figure says.

Cordless Impact Wrench 1/2 Inch: The Default, and Why

1/2 in. is the default drive for general automotive and maintenance work because it covers the widest span of common fasteners with the widest choice of sockets — and because passenger-car wheel nuts sit inside its range.

It is also where the M7 cordless range is deepest, which matters more than it sounds: within one drive size you can pick the tool by weight and torque rather than compromising on socket fit.

Model	Max. torque	Bolt capacity	Weight	Notes
DW-404	900 Nm / 660 ft-lb	M6–M16; nut 10–24 mm	1.16 kg	Lightest 1/2 in.
DW-405	900 Nm / 660 ft-lb	M6–M16	1.2 kg	Brushless, torque-limited
DW-IW400	900 Nm	M6–M16	1.3 kg	—
DW-401	894 Nm / 660 ft-lb	M16; nut 24 mm	1.48 kg	—
DW-C401	1350 Nm	M6–M26	1.7 kg	Widest bolt range under 2 kg
DW-406	1600 Nm / 1200 ft-lb	M10–M25; nut 17–36 mm	2.0 kg (bare)	—
DW-402	1700 Nm / 1250 ft-lb	M10–M24; nut 17–36 mm	3.33 kg	Highest torque at 1/2 in.

Read the bolt capacity column rather than the torque column. The DW-404 and the DW-402 are both 1/2 in. tools, but one is rated from M6 and the other starts at M10 — they are built for different ends of the same drive size.

3/4 in.: When a Cordless Impact Wrench Needs More Drive

Move to 3/4 in. when the fastener requires it, not when more torque sounds like a safer margin.

The DW-601 is rated 1900 Nm / 1400 ft-lb with M10–M27 bolt capacity. That is commercial vehicle wheels, heavy plant and structural fasteners — work where the 1/2 in. socket range runs out before the torque does.

The practical trigger is usually the socket, not the number. If the fasteners on the job need sockets that are only made in 3/4 in. drive, the decision has been made for you.

The weight you carry for the torque

Across the M7 cordless range, drive size and weight move together: 1 kg at 3/8 in., 1.16 kg for the lightest 1/2 in. tool, and 3.37 kg at 3/4 in.

That is more than three times the weight from the smallest to the largest, and the operator carries the difference on every fastener, not just the ones that needed the torque. Two consequences worth planning for:

Overhead and extended-reach work is where weight is felt first. A tool that is comfortable at bench height is a different proposition at arm’s length above the shoulder.
A second, lighter tool often beats one large one. A 1/2 in. tool for the bulk of the work and a 3/4 in. tool brought out for the fasteners that need it is usually less tiring than running the heavy tool all shift.

Weight is also why “buy the biggest one and cover everything” rarely survives contact with a real shift.

Sockets, adaptors and what not to do

Use impact sockets, and use them in the drive size the tool was built for.

Impact sockets only. Chrome hand sockets are not made for repeated hammer blows and can fracture. This is a safety point, not a durability preference.
Do not use a step-up adaptor to reach a larger socket. A 1/2 in. tool with a 1/2-to-3/4 adaptor is still a 1/2 in. tool; the adaptor adds a failure point and the torque does not increase. If the job needs 3/4 in. sockets, it needs a 3/4 in. tool.
A step-down adaptor is the milder case — a larger tool driving smaller sockets — but the tool’s torque now exceeds what the smaller socket and fastener were sized for, so control the setting rather than the grip.
Extensions cost torque. Every joint between anvil and fastener absorbs some of the blow. Keep the stack as short as the access allows.

Matching drive size to the job

Cordless impact wrench drive size guide comparing 3/8 inch, 1/2 inch and 3/4 inch drive sizes — Compare 3/8 in., 1/2 in. and 3/4 in. cordless impact wrench drive sizes at a glance.

The work	Drive	Why
Engine bay, interior, confined access, light assembly	3/8 in.	Tool length decides whether the job is possible; 434 Nm covers the fasteners in that space
Passenger-car wheel nuts, general automotive	1/2 in.	Widest socket availability; every M7 1/2 in. model is rated 894 Nm or above
All-shift maintenance, weight matters	1/2 in.	The DW-404 is 1.16 kg at 900 Nm — the torque is there without the bulk
Larger bolts but still hand-carried	1/2 in.	The DW-C401 reaches M26 bolt capacity at 1.7 kg
Commercial vehicle wheels, heavy plant, structural	3/4 in.	1900 Nm and M10–M27; the socket range at 1/2 in. runs out first
Over-tightening is the risk being managed	1/2 in.	The DW-405 is torque-limited rather than measuring, capping output at a set level

If the work spans more than one row, that is a genuine two-tool answer rather than a compromise. For the full range and how torque and applications fit together, see the cordless impact wrench selection guide; for the air and cordless comparison at each drive size, see air vs electric vs cordless.

Sources and specification notes

Every figure on this page comes from M7’s own published product documentation. Nothing has been converted, rounded or estimated from a comparable model.

Source — the official product page for each model on mighty-seven.com. Every model number links to the page its figures were taken from.
Specifications verified — 17 September 2026. Where M7 revises a datasheet, the product page is the current record.
Dual units — Nm and ft-lb are shown together only where both are printed on the datasheet. Where only one unit is published, only that unit appears.
Weights — bare tool unless the table says otherwise. Weight with a battery fitted depends on which pack is used.
Maximum torque — a laboratory measurement published for comparison between models, not a working figure for a specific joint.
Final torque — set with a calibrated torque wrench to the vehicle or structure manufacturer’s specified value.

For full datasheets, kit contents and models not listed here, request the current M7 catalogue or ask your local distributor.

Frequently Asked Questions

What size impact wrench do I need for lug nuts?

For passenger-car wheel nuts, 1/2 in. drive is the standard choice, and every 1/2 in. model in the M7 cordless range is rated 894 Nm / 660 ft-lb or above. For commercial vehicle wheels, move to 3/4 in. — the DW-601 at 1900 Nm / 1400 ft-lb. Always set the final torque with a torque wrench to the manufacturer’s specified value.

Can I use a 1/2 to 3/4 adaptor instead of buying a 3/4 impact wrench?

An adaptor lets a 3/4 in. socket fit, but it does not increase the tool’s torque and it adds a joint that can fail under repeated impact. If the fasteners need 3/4 in. sockets, they need a tool built for that drive.

Is 3/8 in. too small for automotive work?

Not for the work it is meant for. The M7 DS-204 is rated 434 Nm / 320 ft-lb with an 8–13 mm nut capacity, which covers a great deal of engine bay and interior work where a longer tool simply will not reach. It is not a wheel-nut tool.

What is the difference between bolt capacity and maximum torque?

Maximum torque is the peak the tool can produce under laboratory conditions. Bolt capacity is the fastener range the tool is designed to work on, and it is the more useful figure when specifying. Two tools with the same 900 Nm rating can have different bolt capacities.

Do I need impact sockets, or will normal sockets work?

Impact sockets, without exception. Chrome hand sockets are not built to absorb repeated hammer blows and can fracture in use. Match the socket’s drive size to the tool rather than adapting between sizes.