Screw / Bolt Size Chart
Metric (M) thread pitch, spanner, drill + inch equivalent
Metric bolt chart (KS/ISO)
| Size | Pitch(mm) | Spanner(mm) | Tap drill(mm) | Inch approx |
|---|---|---|---|---|
| M3 | 0.5 | 5.5 | 2.5 | β |
| M4 | 0.7 | 7 | 3.3 | #8 |
| M5 | 0.8 | 8 | 4.2 | #10 |
| M6 | 1.0 | 10 | 5.0 | 1/4" |
| M8 | 1.25 | 13 | 6.8 | 5/16" |
| M10 | 1.5 | 17 | 8.5 | 3/8" |
| M12 | 1.75 | 19 | 10.2 | 1/2" |
| M14 | 2.0 | 22 | 12.0 | 9/16" |
| M16 | 2.0 | 24 | 14.0 | 5/8" |
| M20 | 2.5 | 30 | 17.5 | 3/4" |
β» Coarse-thread pitch. Spanner across-flats for standard hex bolts (varies by maker). Inch equivalents are nearest-diameter, not fully interchangeable.
FAQ
What spanner for an M6 bolt?
A standard M6 hex bolt uses a 10mm spanner; M8=13mm, M10=17mm.
What is M6 in inches?
Nearest diameter is 1/4", though pitch differs so it is not fully compatible.
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