M4 Bolt Size and Thread Specifications
Quick answer
M4 bolts measure 4mm major diameter with 0.7mm coarse pitch in common ISO data.
They bridge small instruments and light machinery hardware lines.
Use the chart for hex and drill sizes, then screw size conversion when you match inch stock.
M4 is a common small metric fastener used in machinery, automotive trim, electronics, and general hardware. A 4 mm nominal diameter with 0.7 mm pitch offers a good balance of strength and compact size. Spanish reference: perno M4. For tap drill size, thread types, and thread identifier workflows, pair this page with tools as you verify threads.
Specifications
| Specification | Value |
|---|---|
| Nominal diameter | 4 mm |
| Standard pitch | 0.7 mm |
| Tap drill size | 3.3 mm |
| Closest imperial equivalent | #8-32 |
Hex head size
| Bolt size | Hex head size |
|---|---|
| M4 | 7 mm |
Common uses
M4 bolts are used in machinery, automotive assemblies, electronics, furniture hardware, and light structural components. They are widely available and easy to source. Cross-check loads with the bolt size chart and screw size conversion when you mix metric and inch bins.
Related tools
Related charts
M4 vs M5 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 M5 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.
M4 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 M4 bolt?
The standard pitch for M4 is 0.7 mm.
What drill size should be used for tapping M4 threads?
For M4 x 0.7 thread, use a 3.3 mm tap drill.
What imperial screw is closest to M4?
#8-32 is the closest imperial equivalent to M4.