ISO Metric Fine Thread Chart
Fine-pitch ISO metric threads from M3×0.35 to M48×3, with basic diameters, tap drill, clearance hole and tensile stress area. A fine thread is always written with its pitch, because a diameter can have up to three of them.
| Thread | Pitch (mm) | Pitch Ø d2 | Minor Ø D1 | Root Ø d3 | Tap drill (mm) | Clearance hole | Stress area (mm²) |
|---|---|---|---|---|---|---|---|
| M3×0.35 | 0.35 | 2.773 | 2.621 | 2.571 | 2.65 | 3.4 | 5.61 |
| M4×0.5 | 0.5 | 3.675 | 3.459 | 3.387 | 3.5 | 4.5 | 9.79 |
| M5×0.5 | 0.5 | 4.675 | 4.459 | 4.387 | 4.5 | 5.5 | 16.1 |
| M6×0.75 | 0.75 | 5.513 | 5.188 | 5.080 | 5.2 | 6.6 | 22.0 |
| M7×0.75 | 0.75 | 6.513 | 6.188 | 6.080 | 6.2 | 7.6 | 31.1 |
| M8×0.75 | 0.75 | 7.513 | 7.188 | 7.080 | 7.2 | 9 | 41.8 |
| M8×1 | 1 | 7.350 | 6.917 | 6.773 | 7 | 9 | 39.2 |
| M9×1 | 1 | 8.350 | 7.917 | 7.773 | 8 | — | 51.0 |
| M10×0.75 | 0.75 | 9.513 | 9.188 | 9.080 | 9.2 | 11 | 67.9 |
| M10×1 | 1 | 9.350 | 8.917 | 8.773 | 9 | 11 | 64.5 |
| M10×1.25 | 1.25 | 9.188 | 8.647 | 8.466 | 8.8 | 11 | 61.2 |
| M12×1 | 1 | 11.350 | 10.917 | 10.773 | 11 | 13.5 | 96.1 |
| M12×1.25 | 1.25 | 11.188 | 10.647 | 10.466 | 10.8 | 13.5 | 92.1 |
| M12×1.5 | 1.5 | 11.026 | 10.376 | 10.160 | 10.5 | 13.5 | 88.1 |
| M14×1 | 1 | 13.350 | 12.917 | 12.773 | 13 | 15.5 | 134 |
| M14×1.25 * | 1.25 | 13.188 | 12.647 | 12.466 | 12.8 | 15.5 | 129 |
| M14×1.5 | 1.5 | 13.026 | 12.376 | 12.160 | 12.5 | 15.5 | 125 |
| M16×1 | 1 | 15.350 | 14.917 | 14.773 | 15 | 17.5 | 178 |
| M16×1.25 * | 1.25 | 15.188 | 14.647 | 14.466 | 14.8 | 17.5 | 173 |
| M16×1.5 | 1.5 | 15.026 | 14.376 | 14.160 | 14.5 | 17.5 | 167 |
| M18×1 | 1 | 17.350 | 16.917 | 16.773 | 17 | 20 | 229 |
| M18×1.5 | 1.5 | 17.026 | 16.376 | 16.160 | 16.5 | 20 | 216 |
| M18×2 | 2 | 16.701 | 15.835 | 15.546 | 16 | 20 | 204 |
| M20×1 | 1 | 19.350 | 18.917 | 18.773 | 19 | 22 | 285 |
| M20×1.5 | 1.5 | 19.026 | 18.376 | 18.160 | 18.5 | 22 | 272 |
| M20×2 | 2 | 18.701 | 17.835 | 17.546 | 18 | 22 | 258 |
| M22×1 | 1 | 21.350 | 20.917 | 20.773 | 21 | 24 | 348 |
| M22×1.5 | 1.5 | 21.026 | 20.376 | 20.160 | 20.5 | 24 | 333 |
| M22×2 | 2 | 20.701 | 19.835 | 19.546 | 20 | 24 | 318 |
| M24×1 | 1 | 23.350 | 22.917 | 22.773 | 23 | 26 | 418 |
| M24×1.5 | 1.5 | 23.026 | 22.376 | 22.160 | 22.5 | 26 | 401 |
| M24×2 | 2 | 22.701 | 21.835 | 21.546 | 22 | 26 | 384 |
| M27×1 | 1 | 26.350 | 25.917 | 25.773 | 26 | 30 | 533 |
| M27×1.5 | 1.5 | 26.026 | 25.376 | 25.160 | 25.5 | 30 | 514 |
| M27×2 | 2 | 25.701 | 24.835 | 24.546 | 25 | 30 | 496 |
| M30×1 | 1 | 29.350 | 28.917 | 28.773 | 29 | 33 | 663 |
| M30×1.5 | 1.5 | 29.026 | 28.376 | 28.160 | 28.5 | 33 | 642 |
| M30×2 | 2 | 28.701 | 27.835 | 27.546 | 28 | 33 | 621 |
| M33×1.5 | 1.5 | 32.026 | 31.376 | 31.160 | 31.5 | 36 | 784 |
| M33×2 | 2 | 31.701 | 30.835 | 30.546 | 31 | 36 | 761 |
| M33×3 * | 3 | 31.051 | 29.752 | 29.319 | 30 | 36 | 716 |
| M36×1.5 | 1.5 | 35.026 | 34.376 | 34.160 | 34.5 | 39 | 940 |
| M36×2 | 2 | 34.701 | 33.835 | 33.546 | 34 | 39 | 915 |
| M36×3 | 3 | 34.051 | 32.752 | 32.319 | 33 | 39 | 865 |
| M39×1.5 | 1.5 | 38.026 | 37.376 | 37.160 | 37.5 | 42 | 1110 |
| M39×2 | 2 | 37.701 | 36.835 | 36.546 | 37 | 42 | 1080 |
| M39×3 | 3 | 37.051 | 35.752 | 35.319 | 36 | 42 | 1030 |
| M42×1.5 | 1.5 | 41.026 | 40.376 | 40.160 | 40.5 | 45 | 1290 |
| M42×2 | 2 | 40.701 | 39.835 | 39.546 | 40 | 45 | 1260 |
| M42×3 | 3 | 40.051 | 38.752 | 38.319 | 39 | 45 | 1210 |
| M45×1.5 | 1.5 | 44.026 | 43.376 | 43.160 | 43.5 | 48 | 1490 |
| M45×2 | 2 | 43.701 | 42.835 | 42.546 | 43 | 48 | 1460 |
| M45×3 | 3 | 43.051 | 41.752 | 41.319 | 42 | 48 | 1400 |
| M48×1.5 | 1.5 | 47.026 | 46.376 | 46.160 | 46.5 | 52 | 1710 |
| M48×2 | 2 | 46.701 | 45.835 | 45.546 | 46 | 52 | 1670 |
| M48×3 | 3 | 46.051 | 44.752 | 44.319 | 45 | 52 | 1600 |
The default pitch for each diameter is in the metric coarse thread chart.
Which fine pitches exist
ISO 261 assigns each diameter a short list of fine pitches rather than one. Up to M7 there is a single fine pitch; from M8 there are two or three. The same few pitches repeat across diameters: 1 mm, 1.5 mm, 2 mm and 3 mm cover almost everything from M8 to M48, which keeps the number of taps and gauges down.
Three entries in this chart carry a warning. M14×1.25 is listed by ISO 261 for spark plugs only, M33×3 is a pitch the standard asks designers to avoid, and M16×1.25 is not in ISO 261 at all.
What a fine pitch changes
At the same diameter a finer pitch makes the thread shallower. The core of the bolt is larger, so the tensile stress area goes up: M12×1.25 has 92.1 mm² against 84.3 mm² for coarse M12, about 9% more. The lead angle is smaller, so the thread resists loosening better and gives finer adjustment per turn. The cost is slower assembly, more sensitivity to damaged or plated threads, and a weaker nut thread in soft materials.
Common questions
What is the tap drill for M10×1.25?
Diameter minus pitch gives 10 − 1.25 = 8.75 mm. Most tap drill tables round this to 8.8 mm, and either drill leaves about 75% thread.
What is the tap drill for M12×1.5?
The tap drill for M12×1.5 is 10.5 mm, which is 12 − 1.5 exactly.
Do fine threads use the same clearance hole?
Yes. The clearance hole depends only on the diameter, so M10×1 and M10×1.5 both use 11 mm in the ISO 273 medium series.
Other charts and tools
Sources: ISO 261 (pitches), ISO 724 (basic dimensions), ISO 273 (clearance holes), ISO 898-1 (stress areas) and tap drill tables based on ISO 2306. How this site checks its data. Last reviewed 29 September 2026.