M3 Bolt Size and Thread Specifications
Quick answer
M3 bolts measure 3mm major diameter with 0.5mm coarse pitch in ISO listings.
They fit electronics, cameras, and light assemblies where space is tight.
Use the tables below for tap drill and hex, then the tap drill calculator for non-standard pitches.
M3 is a small metric fastener used in electronics, small machinery, and precision assemblies. It provides a 3 mm nominal diameter with 0.5 mm pitch and is commonly used where space is limited. Spanish reference: perno M3. For tap drill size, thread types, and thread identifier workflows, pair this page with tools as you verify threads.
Specifications
| Specification | Value |
|---|---|
| Nominal diameter | 3 mm |
| Standard pitch | 0.5 mm |
| Tap drill size | 2.5 mm |
| Closest imperial equivalent | #4-40 |
Hex head size
| Bolt size | Hex head size |
|---|---|
| M3 | 5.5 mm |
Common uses
M3 bolts are common in electronics enclosures, small machinery, cameras, and precision equipment. They are also used in furniture hardware and light structural applications. Cross-check loads with the bolt size chart and screw size conversion when you mix metric and inch bins.
Related tools
Related charts
M3 vs M4 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 M4 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.
M3 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 M3 bolt?
The standard pitch for M3 is 0.5 mm.
What drill size should be used for tapping M3 threads?
For M3 x 0.5 thread, use a 2.5 mm tap drill.
What imperial screw is closest to M3?
#4-40 is the closest imperial equivalent to M3.