M16 thread pitch and dimensions
The M16 thread pitch is 2.0 mm (ISO 261 coarse), about 12.7 threads per inch. Its basic pitch diameter is 14.701 mm and its minor diameter is 13.835 mm in the nut and 13.546 mm on the bolt (ISO 724 / ISO 898-1).
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| Dimension | Formula | mm | inch |
|---|---|---|---|
| Major diameter d | nominal | 16.000 | 0.6299 |
| Pitch P | ISO 261 | 2.000 | 0.0787 |
| Pitch diameter d2 | d − 0.649519 P | 14.701 | 0.5788 |
| Minor diameter D1 (nut) | d − 1.082532 P | 13.835 | 0.5447 |
| Minor diameter d3 (bolt) | d − 1.226869 P | 13.546 | 0.5333 |
| Fundamental triangle H | 0.866025 P | 1.732 | 0.0682 |
| Thread overlap H1 | 0.541266 P | 1.083 | 0.0426 |
| Thread | Pitch | Series | Pitch Ø d2 | Stress area As | Tap drill |
|---|---|---|---|---|---|
| M16 x 2.0 (this page) | 2.0 mm | coarse | 14.701 mm | 157 mm² | 14.0 mm |
| M16 x 1.5 | 1.5 mm | fine | 15.026 mm | 167 mm² | 14.5 mm |
| Thread | Pitch | Minor Ø nut D1 | Stress area As | Hex AF |
|---|---|---|---|---|
| M12 x 1.75 | 1.75 mm | 10.106 mm | 84.3 mm² | 18.0 mm |
| M14 x 2.0 | 2.0 mm | 11.835 mm | 115 mm² | 21.0 mm |
| M16 x 2.0 (this page) | 2.0 mm | 13.835 mm | 157 mm² | 24.0 mm |
| M18 x 2.5 | 2.5 mm | 15.294 mm | 192 mm² | 27.0 mm |
| M20 x 2.5 | 2.5 mm | 17.294 mm | 245 mm² | 30.0 mm |
Practical notes
Metric threads are named by major diameter and pitch: M16 x 2.0 means a 16 mm nominal diameter with 2.0 mm between crests. When no pitch is written (just "M16"), the ISO 261 coarse pitch is meant.
The pitch diameter and minor diameters above are basic (zero-tolerance) sizes. Real nuts and bolts are made to a tolerance class, usually 6H for the nut and 6g for the bolt (ISO 965), so a measured bolt is slightly under these values.
To identify a thread, measure the major diameter with calipers and the pitch with a thread gauge, or count crests over 10 mm. M16 x 2.0 has about 12.7 threads per inch, which is close to, but not the same as, any Unified thread; an inch nut will not run on it.
Tensile stress area As is what bolt strength is calculated on (proof load = As × proof stress for the property class in ISO 898-1). For M16 x 2.0 it is 157 mm².
FAQ
What is the pitch of an M16 thread?
The standard (coarse) pitch of M16 is 2.0 mm per ISO 261. Fine pitches also exist: 1.5 mm.
What is the minor diameter of M16 x 2.0?
The basic minor diameter is 13.835 mm for the internal thread (nut, D1 = d − 1.082532 P) and 13.546 mm for the external thread (bolt, d3 = d − 1.226869 P).
What is the tensile stress area of M16 x 2.0?
As = π/4 × ((d2 + d3)/2)² = 157 mm² for M16 x 2.0 (ISO 898-1).
What tap drill does M16 x 2.0 need?
14.0 mm for a cut tap (major diameter minus pitch, ISO 2306), which gives about 77% thread.
What spanner size fits an M16 bolt?
ISO 4032 nuts and ISO 4014/4017 bolts in M16 are 24.0 mm across flats. Older DIN 934/933 parts can differ at M10, M12, M14 and M22.
Sources: ISO 261 — ISO general purpose metric screw threads, general plan (pitch series) · ISO 724 — ISO general purpose metric screw threads, basic dimensions · ISO 898-1 — mechanical properties of fasteners (minor diameter d3, tensile stress area As) · ISO 4032 / ISO 4014 — hexagon nuts and bolts (width across flats)
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