Interactive thread finder
Find a Metric Bolt Thread Size
Choose a designation or enter measured diameter and pitch to find the closest listed metric thread.
Use a thread-pitch gauge when possible. The closest-match result is an identification aid, not a tolerance inspection.
- Designation
- M10 × 1.5
- Nominal major diameter, d
- 10.000 mm
- Pitch, P
- 1.500 mm
- Basic pitch diameter, d₂
- 9.026 mm
- Basic internal minor diameter, D₁
- 8.376 mm
- Basic external minor diameter, d₃
- 8.160 mm
- Fundamental triangle height, H
- 1.299 mm
- Lead, L (single-start)
- 1.500 mm/rev
Basic dimensions only
These values describe the ideal ISO metric thread profile. Manufacturing limits depend on the specified tolerance class, internal or external thread, coating, plating, and the applicable ISO 965 requirements.
Searchable reference
Metric Bolt Thread Sizes and Basic Dimensions
Representative commercial metric bolt-thread combinations with dimensions calculated from the ISO basic profile.
Search by designation, diameter, pitch, or series. Choose View to synchronize the diagram and result panel.
No listed metric threads match the current search and filters.
| View | Thread | Series | Basic dimensions and conversion | Preferred coarse | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| M2 × 0.4 | Coarse | 2 | 0.4 | 1.740 | 1.567 | 1.509 | 0.4 | 63.50 | Yes | |
| M2 × 0.25 | Fine | 2 | 0.25 | 1.838 | 1.729 | 1.693 | 0.25 | 101.60 | No | |
| M2.5 × 0.45 | Coarse | 2.5 | 0.45 | 2.208 | 2.013 | 1.948 | 0.45 | 56.44 | Yes | |
| M2.5 × 0.35 | Fine | 2.5 | 0.35 | 2.273 | 2.121 | 2.071 | 0.35 | 72.57 | No | |
| M3 × 0.5 | Coarse | 3 | 0.5 | 2.675 | 2.459 | 2.387 | 0.5 | 50.80 | Yes | |
| M3 × 0.35 | Fine | 3 | 0.35 | 2.773 | 2.621 | 2.571 | 0.35 | 72.57 | No | |
| M4 × 0.7 | Coarse | 4 | 0.7 | 3.545 | 3.242 | 3.141 | 0.7 | 36.29 | Yes | |
| M4 × 0.5 | Fine | 4 | 0.5 | 3.675 | 3.459 | 3.387 | 0.5 | 50.80 | No | |
| M5 × 0.8 | Coarse | 5 | 0.8 | 4.480 | 4.134 | 4.019 | 0.8 | 31.75 | Yes | |
| M5 × 0.5 | Fine | 5 | 0.5 | 4.675 | 4.459 | 4.387 | 0.5 | 50.80 | No | |
| M6 × 1 | Coarse | 6 | 1 | 5.350 | 4.917 | 4.773 | 1 | 25.40 | Yes | |
| M6 × 0.75 | Fine | 6 | 0.75 | 5.513 | 5.188 | 5.080 | 0.75 | 33.87 | No | |
| M6 × 0.5 | Extra fine | 6 | 0.5 | 5.675 | 5.459 | 5.387 | 0.5 | 50.80 | No | |
| M8 × 1.25 | Coarse | 8 | 1.25 | 7.188 | 6.647 | 6.466 | 1.25 | 20.32 | Yes | |
| M8 × 1 | Fine | 8 | 1 | 7.350 | 6.917 | 6.773 | 1 | 25.40 | No | |
| M8 × 0.75 | Extra fine | 8 | 0.75 | 7.513 | 7.188 | 7.080 | 0.75 | 33.87 | No | |
| M10 × 1.5 | Coarse | 10 | 1.5 | 9.026 | 8.376 | 8.160 | 1.5 | 16.93 | Yes | |
| M10 × 1.25 | Fine | 10 | 1.25 | 9.188 | 8.647 | 8.466 | 1.25 | 20.32 | No | |
| M10 × 1 | Extra fine | 10 | 1 | 9.350 | 8.917 | 8.773 | 1 | 25.40 | No | |
| M12 × 1.75 | Coarse | 12 | 1.75 | 10.863 | 10.106 | 9.853 | 1.75 | 14.51 | Yes | |
| M12 × 1.5 | Fine | 12 | 1.5 | 11.026 | 10.376 | 10.160 | 1.5 | 16.93 | No | |
| M12 × 1.25 | Fine | 12 | 1.25 | 11.188 | 10.647 | 10.466 | 1.25 | 20.32 | No | |
| M12 × 1 | Extra fine | 12 | 1 | 11.350 | 10.917 | 10.773 | 1 | 25.40 | No | |
| M14 × 2 | Coarse | 14 | 2 | 12.701 | 11.835 | 11.546 | 2 | 12.70 | Yes | |
| M14 × 1.5 | Fine | 14 | 1.5 | 13.026 | 12.376 | 12.160 | 1.5 | 16.93 | No | |
| M14 × 1.25 | Fine | 14 | 1.25 | 13.188 | 12.647 | 12.466 | 1.25 | 20.32 | No | |
| M16 × 2 | Coarse | 16 | 2 | 14.701 | 13.835 | 13.546 | 2 | 12.70 | Yes | |
| M16 × 1.5 | Fine | 16 | 1.5 | 15.026 | 14.376 | 14.160 | 1.5 | 16.93 | No | |
| M16 × 1 | Extra fine | 16 | 1 | 15.350 | 14.917 | 14.773 | 1 | 25.40 | No | |
| M18 × 2.5 | Coarse | 18 | 2.5 | 16.376 | 15.294 | 14.933 | 2.5 | 10.16 | Yes | |
| M18 × 2 | Fine | 18 | 2 | 16.701 | 15.835 | 15.546 | 2 | 12.70 | No | |
| M18 × 1.5 | Fine | 18 | 1.5 | 17.026 | 16.376 | 16.160 | 1.5 | 16.93 | No | |
| M20 × 2.5 | Coarse | 20 | 2.5 | 18.376 | 17.294 | 16.933 | 2.5 | 10.16 | Yes | |
| M20 × 2 | Fine | 20 | 2 | 18.701 | 17.835 | 17.546 | 2 | 12.70 | No | |
| M20 × 1.5 | Fine | 20 | 1.5 | 19.026 | 18.376 | 18.160 | 1.5 | 16.93 | No | |
| M22 × 2.5 | Coarse | 22 | 2.5 | 20.376 | 19.294 | 18.933 | 2.5 | 10.16 | Yes | |
| M22 × 2 | Fine | 22 | 2 | 20.701 | 19.835 | 19.546 | 2 | 12.70 | No | |
| M22 × 1.5 | Fine | 22 | 1.5 | 21.026 | 20.376 | 20.160 | 1.5 | 16.93 | No | |
| M24 × 3 | Coarse | 24 | 3 | 22.051 | 20.752 | 20.319 | 3 | 8.47 | Yes | |
| M24 × 2 | Fine | 24 | 2 | 22.701 | 21.835 | 21.546 | 2 | 12.70 | No | |
| M24 × 1.5 | Fine | 24 | 1.5 | 23.026 | 22.376 | 22.160 | 1.5 | 16.93 | No | |
| M27 × 3 | Coarse | 27 | 3 | 25.051 | 23.752 | 23.319 | 3 | 8.47 | Yes | |
| M27 × 2 | Fine | 27 | 2 | 25.701 | 24.835 | 24.546 | 2 | 12.70 | No | |
| M27 × 1.5 | Fine | 27 | 1.5 | 26.026 | 25.376 | 25.160 | 1.5 | 16.93 | No | |
| M30 × 3.5 | Coarse | 30 | 3.5 | 27.727 | 26.211 | 25.706 | 3.5 | 7.26 | Yes | |
| M30 × 3 | Fine | 30 | 3 | 28.051 | 26.752 | 26.319 | 3 | 8.47 | No | |
| M30 × 2 | Fine | 30 | 2 | 28.701 | 27.835 | 27.546 | 2 | 12.70 | No | |
| M30 × 1.5 | Fine | 30 | 1.5 | 29.026 | 28.376 | 28.160 | 1.5 | 16.93 | No | |
| M33 × 3.5 | Coarse | 33 | 3.5 | 30.727 | 29.211 | 28.706 | 3.5 | 7.26 | Yes | |
| M33 × 2 | Fine | 33 | 2 | 31.701 | 30.835 | 30.546 | 2 | 12.70 | No | |
| M36 × 4 | Coarse | 36 | 4 | 33.402 | 31.670 | 31.093 | 4 | 6.35 | Yes | |
| M36 × 3 | Fine | 36 | 3 | 34.051 | 32.752 | 32.319 | 3 | 8.47 | No | |
| M36 × 2 | Fine | 36 | 2 | 34.701 | 33.835 | 33.546 | 2 | 12.70 | No | |
| M42 × 4.5 | Coarse | 42 | 4.5 | 39.077 | 37.129 | 36.479 | 4.5 | 5.64 | Yes | |
| M42 × 3 | Fine | 42 | 3 | 40.051 | 38.752 | 38.319 | 3 | 8.47 | No | |
| M48 × 5 | Coarse | 48 | 5 | 44.752 | 42.587 | 41.866 | 5 | 5.08 | Yes | |
| M48 × 3 | Fine | 48 | 3 | 46.051 | 44.752 | 44.319 | 3 | 8.47 | No | |
| M56 × 5.5 | Coarse | 56 | 5.5 | 52.428 | 50.046 | 49.252 | 5.5 | 4.62 | Yes | |
| M56 × 4 | Fine | 56 | 4 | 53.402 | 51.670 | 51.093 | 4 | 6.35 | No | |
| M64 × 6 | Coarse | 64 | 6 | 60.103 | 57.505 | 56.639 | 6 | 4.23 | Yes | |
| M64 × 4 | Fine | 64 | 4 | 61.402 | 59.670 | 59.093 | 4 | 6.35 | No | |
The table is an original transformed reference of representative combinations. Calculated dimensions are basic-profile values rounded for display and are not tolerance limits or acceptance criteria.
Table tools and filters
How to Read a Metric Bolt Thread
M10 × 1.5 identifies a metric thread with a nominal 10 mm major diameter and 1.5 mm axial spacing between adjacent thread crests. When pitch is omitted in ordinary fastener notation, a coarse pitch is often implied, but the drawing or specification should control.
Key takeaways
What the Chart Tells You
- Diameter and pitch define the designation. M10 × 1.25 and M10 × 1.5 have the same nominal diameter but are not interchangeable.
- Pitch diameter controls functional fit. It is the diameter where thread ridge and groove widths are theoretically equal.
- Basic dimensions are not tolerances. Use the specified tolerance class and applicable limits for machining, inspection, or acceptance.
- TPI is only a conversion aid. Metric threads remain designated by pitch in millimetres.
Metric Thread Dimensions and Formulas
The calculator uses the ideal 60-degree ISO metric basic profile. It keeps full internal precision and rounds displayed dimensions to three decimal places.
H is the height of the fundamental equilateral triangle and P is pitch.
The basic pitch diameter is common to the mating ideal profiles.
Basic minor diameter of the internal thread.
Basic minor diameter of the external thread design profile.
Symbols
- d, DBasic major diameter, mm
- PPitch, mm
- d₂, D₂Basic pitch diameter, mm
- D₁Internal-thread basic minor diameter, mm
- d₃External-thread basic minor diameter, mm
How to Identify an Unknown Metric Thread
- Clean the thread and check for damage, plating buildup, or flattened crests.
- Measure the external major diameter across the crests with calipers.
- Measure pitch with a metric thread-pitch gauge. If unavailable, measure several crest spacings and divide by the number of intervals.
- Enter both measurements in the thread finder and compare the reported diameter and pitch differences.
- Confirm the candidate with a known mating part, GO/NO-GO gauge, or the drawing’s tolerance-class requirements.
Example: M10 × 1.5
A nominal diameter near 10 mm and a measured pitch near 1.50 mm points to M10 × 1.5. Its calculated basic pitch diameter is 9.026 mm.
Sanity check: 25.4 ÷ 1.5 = 16.93 TPI, but the proper designation remains metric.
Example: M8 × 1.0
An outside diameter near 8 mm with 1.00 mm crest spacing indicates an M8 fine thread, not the common M8 × 1.25 coarse thread.
Governing limitation: Caliper diameter alone cannot distinguish these two pitches.
Metric Coarse vs Fine Threads
Coarse threads
- Commonly stocked and easier to identify.
- Greater pitch and deeper thread form.
- Often preferred for general assembly and softer materials.
- More tolerant of dirt, minor damage, and rapid installation.
Fine threads
- Smaller pitch provides finer axial adjustment.
- Larger tensile stress area for the same nominal diameter.
- May suit thin-wall or limited-engagement applications when properly designed.
- More sensitive to damage, contamination, and cross-threading.
Selection rule
- Follow the drawing, equipment specification, or governing product standard.
- Do not substitute pitch based only on matching diameter.
- Evaluate preload, fatigue, material strength, engagement, coating, and service environment separately.
Basic Dimensions vs Thread Tolerances
A basic dimension is the exact theoretical size from which limits and deviations are applied. A real bolt or nut is manufactured within a tolerance zone, commonly identified by a class such as 6g for an external thread or 6H for an internal thread.
Do not use this chart as a GO/NO-GO limit table
Acceptance requires the correct tolerance class, standard edition, coating allowance, gauging practice, and product specification. The chart intentionally does not reproduce copyrighted ISO tolerance tables.
Engineering Basis and Data Scope
Representative M2–M64 commercial thread combinations; calculated basic dimensions; no tolerance-limit table or complete ISO dataset.
The page uses the current ISO metric-thread profile and basic-dimension framework. ISO standards are copyrighted, so this page provides an original explanatory diagram, calculated dimensions, and a limited representative reference rather than reproducing the standards.
- ISO 68-1:2023 — Basic and design profilesSupports the 60-degree ISO metric thread profile used by the diagram and equations.
- ISO 724:2023 — Basic dimensionsSupports the basic-dimension framework for ISO metric fastening screw threads.
- ISO 262:2023 — Selected commercial fastener sizesSupports the commercial bolt, screw, stud, and nut thread scope from 1 mm through 100 mm.
Dataset and Review Details
- Publisher
- Turn2Engineering
- Generated
- August 3, 2026
- Dataset label
- metric-thread-reference-v1.0.0
- Units
- Millimetres; TPI shown only as a conversion
- Calculation precision
- Full floating-point precision; three decimals displayed
- Rights status
- Original calculations and diagram; ISO source tables not reproduced in full
- Excluded
- Tolerance limits, gauging limits, multi-start threads, trapezoidal threads, and product-specific head dimensions
- Use
- Educational lookup and preliminary identification
Metric Bolt Thread FAQs
It identifies an ISO metric thread with a nominal 10 mm major diameter and a 1.5 mm pitch measured axially from one thread crest to the next.
M10 × 1.5 is the commonly encountered coarse designation, but M10 also exists in finer pitches such as 1.25 mm and 1.0 mm, so verify the actual specification.
No. Pitch diameter is the theoretical cylinder where thread and groove widths are equal, while minor diameter is measured at the thread roots.
Measure the pitch and compare it with the available pitches for the same nominal diameter; the coarse series has the largest commonly selected pitch for that diameter.
No. Manufacturing and inspection require the specified tolerance class, resulting limits of size, tooling allowance, coating effects, and appropriate gauges.
Use the Diameter and Pitch Together
A metric bolt thread is not fully identified by diameter alone. Confirm the nominal diameter and pitch, use the diagram to understand each basic dimension, and consult the controlling tolerance and product standards before machining, inspecting, or approving a threaded component.