M11 Bolt Size and Thread Specifications
Quick answer
M11 bolts use 11mm major diameter with 1.5mm coarse pitch in standard references.
They are less common than M10 but appear in some machinery lines.
Use the tables below and thread types when you compare coarse and fine series.
M11 is less common than M10 or M12. Check fastener catalogs for nuts, washers, and tools before relying on M11 in new designs. Spanish reference: perno M11. For tap drill size, thread types, and thread identifier workflows, pair this page with tools as you verify threads.
Specifications
| Specification | Value |
|---|---|
| Nominal diameter | 11 mm |
| Standard pitch (coarse) | 1.5 mm |
| Fine pitch | 1.25 mm |
| Tap drill size | 9.5 mm |
| Closest imperial equivalent | 7/16-14 (approx.) |
Hex head size
| Bolt size | Hex head size |
|---|---|
| M11 | 18 mm |
Common uses
Special machinery, some automotive and industrial spares that specify M11. Cross-check loads with the bolt size chart and screw size conversion when you mix metric and inch bins.
Related tools
Related charts
M11 vs M12 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 M12 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.
M11 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 M11 bolt?
The common coarse pitch for M11 is 1.5 mm. Fine pitch is often 1.25 mm where specified.
What drill size should be used for tapping M11 threads?
For M11 x 1.5 coarse thread, use approximately a 9.5 mm tap drill. Use our Tap Drill Calculator for other pitches.
What imperial fastener is closest to M11?
7/16-14 (approx.) is a practical reference for comparing M11 to inch hardware; verify fit for your application.