M12 Bolt Size and Thread Specifications
Quick answer
M12 bolts use 12mm major diameter with 1.75mm coarse pitch and a 10.2mm tap drill.
They are widely used in structural steel, machinery, and automotive work.
Use the chart below and the thread identifier when field measurements differ from tables.
M12 is a large metric bolt size used in structural, automotive, and heavy machinery applications. A 12 mm nominal diameter with 1.75 mm pitch provides high strength and is common in flanges and critical joints. Spanish reference: perno M12. For tap drill size, thread types, and thread identifier workflows, pair this page with tools as you verify threads.
Specifications
| Specification | Value |
|---|---|
| Nominal diameter | 12 mm |
| Standard pitch | 1.75 mm |
| Fine pitch | 1.5 mm |
| Tap drill size | 10.2 mm |
| Closest imperial equivalent | 1/2-13 |
Hex head size
| Bolt size | Hex head size |
|---|---|
| M12 | 19 mm |
Common uses
M12 bolts are used in structural connections, automotive suspension and drivetrain, machinery flanges, and anywhere high clamp force is required. They are standard in many industrial and automotive specifications. Cross-check loads with the bolt size chart and screw size conversion when you mix metric and inch bins.
Related tools
Related charts
M12 vs M14 bolt size
Shank diameter and pitch set tap drill, hex key, and strength for each ISO size. Compare values in the tables above with the M14 bolt size page when you resize hardware.
Use the bolt size chart when you compare hex and shank columns across sizes.
Metric vs UNC thread size
Metric threads list diameter in millimeters and pitch in millimeters per thread; UNC lists nominal inch diameter and threads per inch. They are not interchangeable—taps, dies, and gauges differ.
Read metric vs unc thread context when series labels are unclear.
Use screw size conversion when you must match stocked parts.
M12 specifications and tools
How to choose the right bolt size
Choosing the correct bolt size depends on load, material, and thread type. Larger diameters increase strength, while thread pitch affects holding force.
Use the bolt size chart to compare shank and hex dimensions before you standardize hardware.
Use tap drill size guidance when you plan tapped holes.
Use the thread identifier when stamped sizes are missing.
FAQ
What is the standard pitch for an M12 bolt?
The standard pitch for M12 is 1.75 mm. Fine pitch is 1.5 mm.
What drill size should be used for tapping M12 threads?
For M12 x 1.75 coarse thread, use a 10.2 mm tap drill. Use our Tap Drill Calculator for other pitches.
What imperial bolt is closest to M12?
1/2-13 UNC is the closest imperial equivalent to M12.