When you search for 1 1/2 socket dimensions, you are likely looking for one of two things: the socket size that fits a 1.5-inch fastener head, or the dimensions of a 1-1/2 inch drive system. For most DIYers and mechanics, the first meaning is what matters.
What Does “1 1/2 Socket” Actually Mean?
The term can refer to the socket size, which is the hex opening that fits a fastener, or the drive size, which is the square hole that connects to a ratchet. The socket size meaning is far more common for everyday work, but understanding both prevents a costly mismatch.
Socket size.
Drive size. The square-drive hole that accepts the ratchet. Common drive sizes are 1/4 inch, 3/8 inch, 1/2 inch, and 3/4 inch. A 1-1/2 inch drive exists as an industrial standard — the ASA B5.38 1958 published square-drive standard covers its dimensions — but it is not something a home mechanic encounters. The fastest way to tell them apart: measure the hex opening for socket size, or the square hole on the back for drive size.
Common SAE Socket Sizes and Where 1-1/2 Inch Fits
The standard SAE socket scale runs from small ignition sizes up to 1-1/2 inches. This table shows the full consumer range so you can see where the 1-1/2 inch socket lands and which drive sizes pair with each.
| SAE Size | mm Equivalent | Typical Drive Size |
|---|---|---|
| 1/4 in | 6.35 mm | 1/4 in |
| 5/16 in | 7.94 mm | 1/4 in |
| 3/8 in | 9.53 mm | 3/8 in |
| 1/2 in | 12.7 mm | 3/8 in or 1/2 in |
| 9/16 in | 14.29 mm | 3/8 in or 1/2 in |
| 5/8 in | 15.88 mm | 3/8 in or 1/2 in |
| 11/16 in | 17.46 mm | 3/8 in or 1/2 in |
| 3/4 in | 19.05 mm | 1/2 in |
| 7/8 in | 22.23 mm | 1/2 in |
| 1 in | 25.4 mm | 1/2 in |
| 1-1/4 in | 31.75 mm | 1/2 in |
| 1-1/2 in | 38.1 mm | 1/2 in or 3/4 in |
If you are looking to buy one, our roundup of the best 1 1/2 socket options can help you find the right tool for the job.
How to Avoid Mistakes When Using Large Sockets
Three errors cause most of the trouble with 1-1/2 inch sockets and other large sizes. Knowing them saves you from rounding a bolt or damaging a socket.
Confusing socket size with drive size. The measurement that matters for your fastener is the hex opening, not the square drive. Always measure the bolt head across the flats with a caliper or ruler, and match that number to the socket size — not to the ratchet connection.
Assuming 1-1/2 inch has a direct metric match. The metric conversion is 38.1 mm, which is not a standard metric socket size. Do not force a 38 mm or 39 mm metric socket onto a 1.5-inch SAE fastener — neither will fit correctly, and either can strip the bolt head.
Mixing SAE and metric hardware on the same job. If your fastener is SAE, use an SAE socket. If it is metric, use a metric socket. The difference between a 1-1/2 inch SAE socket and a 38 mm metric socket is small but enough to cause damage under torque. Test fit before applying force — the socket should slide on snugly with no wobble. If it feels loose or will not seat, stop and double-check your measurement.
FAQs
Is a 1-1/2 inch socket the same as 38 mm?
No. Always match the socket to the fastener’s actual measurement, not a rounded conversion.
What drive size do I need for a 1-1/2 inch socket?
The 1/2-inch drive is common in standard tool sets and works for most jobs, while 3/4-inch drive handles higher torque and is safer for heavy-duty use. Check the socket’s square-drive hole before purchasing a ratchet.
Can I use a 1-1/2 inch socket with an impact wrench?
Only if the socket is rated for impact use. Impact sockets are made from tougher steel and resist shattering under the hammering action of an impact tool. A standard chrome socket used on an impact wrench can crack or shatter, causing injury. Look for “impact” marked on the socket body.
References & Sources
- Engineers Edge. “Square Drive Tools Dimensions.” Reproduces the ASA B5.38 1958 standard for 1-1/2 inch drive dimensions.