Working on heavy equipment, trucks, or tractors means straddling the SAE and metric worlds. If you’ve searched for what a 1 1/2 socket is in metric to grab the right tool from your box, the exact answer is 38.1 mm. Since no standard metric set includes a 38.1 mm socket, the closest practical equivalent is 39 mm. Understanding this difference stops you from rounding a bolt or damaging a fastener under torque.
What Is The Metric Equivalent Of A 1 1/2 Socket?
Because standard metric sockets jump by whole millimeters, a 39 mm socket is the closest readily available fit, though it is 0.9 mm larger than the true SAE size.
| Attribute | Value |
|---|---|
| SAE Size | 1-1/2 in (1.5 in) |
| Exact Metric Conversion | 38.10 mm |
| Closest Standard Metric Socket | 39 mm |
| Typical Drive Size | 1-inch drive |
| Standard Point Type | 12-point |
Per standard inch-to-metric conversion charts, this formula is universal. Always confirm by checking the stamp on the socket side — “1-1/2” for SAE or “39mm” for the metric alternative.
Drive Size vs. Socket Size: Clearing Up A Common Confusion
A frequent mistake is seeing “1/2” in “1-1/2” and assuming it is a 1/2-inch drive socket. The “1-1/2” refers exclusively to the opening size — the width of the fastener it fits. The drive size, where the ratchet or breaker bar attaches, is almost always 1 inch for a standard 1½-inch socket.
This distinction is critical when shopping for tools. A 1/2-inch drive ratchet is far too small for a socket this large. Pairing a 1½-inch socket with the correct 1-inch drive handle ensures the tool can handle the high torque required for heavy-duty truck and equipment work.
How To Choose Between A 1 1/2 SAE Socket And A 39 mm Socket
While 39 mm is the closest metric equivalent, it is not a perfect substitute in every situation. For high-torque applications like semi-truck lug nuts or suspension bolts, using the exact SAE socket is safer, as the 0.9 mm gap in the 39 mm socket can cause slippage and rounding under load.
For a full roundup of the best 1-1/2 inch socket options currently on the market, check out our detailed guide. If the 39 mm socket is the only option on hand, slide it onto the fastener first — it should engage the flats without rocking. If it feels loose, switch to the exact SAE size.
FAQs
Is a 1 1/2 socket the same as a 38mm socket?
No. A 38 mm socket is 0.1 mm too small and will not fit the fastener. The closest standard metric socket that fits is 39 mm.
What is a 1 1/2 socket used for?
It is designed for large, heavy-duty fasteners found on trucks, buses, tractors, and construction equipment — specifically axle nuts, lug nuts, and suspension bolts.
What drive size is a 1 1/2 socket?
Standard 1½-inch sockets typically use a 1-inch drive. Always verify by looking at the stamped markings on the socket. Some shorter, low-profile variants use a 3/4-inch drive.
References & Sources
- Engineering Toolbox. “Wrenches – Inches and Metric Conversion Chart.” Provides the standard conversion multiplier (25.4) and comparative socket sizes.