Metric Thread Pitch Chart — Coarse & Fine
Contents
Quick metric thread pitch lookup
Use the chart to search common ISO metric commercial fastener sizes from M1.6 through M64. It shows the preferred coarse series, selected fine-pitch options, and a threads-per-inch equivalent for the coarse pitch. The TPI value is an informational conversion; it does not turn a metric thread into an inch thread.
Metric Thread Pitch Chart — Coarse and Fine
Selected ISO metric commercial fastener thread sizes from M1.6 through M64, with coarse pitch, common fine-pitch options, and an informational threads-per-inch conversion.
Showing 28 of 28 rows.
| M1.6 | 1.6 | 0.35 | 0.2 | 72.57 | Coarse pitch is the normal designation when no pitch is appended. |
|---|---|---|---|---|---|
| M2 | 2 | 0.4 | 0.25 | 63.5 | Coarse pitch is the normal designation when no pitch is appended. |
| M2.5 | 2.5 | 0.45 | 0.35 | 56.44 | Coarse pitch is the normal designation when no pitch is appended. |
| M3 | 3 | 0.5 | 0.35 | 50.8 | Coarse pitch is the normal designation when no pitch is appended. |
| M4 | 4 | 0.7 | 0.5 | 36.29 | Coarse pitch is the normal designation when no pitch is appended. |
| M5 | 5 | 0.8 | 0.5 | 31.75 | Coarse pitch is the normal designation when no pitch is appended. |
| M6 | 6 | 1 | 0.75 | 25.4 | Coarse pitch is the normal designation when no pitch is appended. |
| M8 | 8 | 1.25 | 1 / 0.75 | 20.32 | M8 fine options commonly include 1.00 and 0.75 mm. |
| M10 | 10 | 1.5 | 1.25 / 1 | 16.93 | M10 fine options commonly include 1.25 and 1.00 mm. |
| M12 | 12 | 1.75 | 1.5 / 1.25 | 14.51 | M12 fine options commonly include 1.50 and 1.25 mm. |
| M14 | 14 | 2 | 1.5 | 12.7 | Coarse pitch is the normal designation when no pitch is appended. |
| M16 | 16 | 2 | 1.5 | 12.7 | Coarse pitch is the normal designation when no pitch is appended. |
| M18 | 18 | 2.5 | 2 / 1.5 | 10.16 | M18 fine options commonly include 2.00 and 1.50 mm. |
| M20 | 20 | 2.5 | 2 / 1.5 | 10.16 | M20 fine options commonly include 2.00 and 1.50 mm. |
| M22 | 22 | 2.5 | 2 / 1.5 | 10.16 | M22 fine options commonly include 2.00 and 1.50 mm. |
| M24 | 24 | 3 | 2 | 8.47 | Coarse pitch is the normal designation when no pitch is appended. |
| M27 | 27 | 3 | 2 | 8.47 | Coarse pitch is the normal designation when no pitch is appended. |
| M30 | 30 | 3.5 | 2 | 7.26 | Coarse pitch is the normal designation when no pitch is appended. |
| M33 | 33 | 3.5 | 2 | 7.26 | Coarse pitch is the normal designation when no pitch is appended. |
| M36 | 36 | 4 | 3 | 6.35 | Coarse pitch is the normal designation when no pitch is appended. |
| M39 | 39 | 4 | 3 | 6.35 | Coarse pitch is the normal designation when no pitch is appended. |
| M42 | 42 | 4.5 | 3 | 5.64 | Coarse pitch is the normal designation when no pitch is appended. |
| M45 | 45 | 4.5 | 3 | 5.64 | Coarse pitch is the normal designation when no pitch is appended. |
| M48 | 48 | 5 | 3 | 5.08 | Coarse pitch is the normal designation when no pitch is appended. |
| M52 | 52 | 5 | 4 | 5.08 | Coarse pitch is the normal designation when no pitch is appended. |
| M56 | 56 | 5.5 | 4 | 4.62 | Coarse pitch is the normal designation when no pitch is appended. |
| M60 | 60 | 5.5 | 4 | 4.62 | Coarse pitch is the normal designation when no pitch is appended. |
| M64 | 64 | 6 | 4 | 4.23 | Coarse pitch is the normal designation when no pitch is appended. |
Use this chart carefully: Use the complete thread designation, including pitch, when ordering or matching a fastener. A diameter match alone does not prove that two threads are compatible.
Sources and method
Dimensions are based on the sources below. Verify the current specification for production-critical work.
- ISO 262:2023 — Edition 3, published 2023-04. Controlling source for selected commercial fastener diameter/pitch combinations.
- ISO 261:1998 — Edition 2, published 1998-12; confirmed current in 2024. General plan for ISO metric screw-thread diameter and pitch combinations.
- Bossard Metric ISO Threads technical reference — F-en-2023.05. Public manufacturer reference used to cross-check representative ISO coarse and fine rows.
- Pitch-to-TPI formula v1 — Formula registry v1. Informational inch conversion; it does not change the metric thread designation.
The chart lists selected standard diameter-and-pitch combinations. It does not list every mathematically possible pitch, every specialty automotive or instrument thread, or every manufacturer-specific combination. If a drawing or supplier catalog gives a complete designation such as M12 × 1.25, use that designation instead of selecting a pitch from diameter alone.
What does M10 × 1.5 mean?
M10 identifies a nominal outside diameter of 10 mm. 1.5 identifies a pitch of 1.5 mm, which is the axial distance from one thread crest to the next. The designation is incomplete if it says only M10 and the application could use more than one pitch. In ordinary fastener language, M10 without an appended pitch normally refers to the preferred coarse series shown in the chart.
| Part of designation | Meaning | Example |
|---|---|---|
| M | ISO metric screw-thread system | M |
| Nominal diameter | Nominal thread diameter in millimetres | 10 |
| Pitch | Distance between adjacent thread crests in millimetres | 1.5 |
| Complete designation | System, diameter, and pitch together | M10 × 1.5 |
Coarse versus fine metric threads
The preferred coarse pitch is usually the easiest option to source and identify. It is common in general-purpose bolts, screws, nuts, and standard hardware. The larger pitch also advances farther per turn, which can make assembly faster and less sensitive to small amounts of contamination.
Fine threads use a smaller pitch for the same nominal diameter. They can provide more adjustment per revolution and more thread engagement over a given axial length. They can also help when a design has limited wall thickness or needs a smaller change in position during adjustment. These benefits do not mean that fine threads are always stronger or always better. Joint strength, stripping resistance, preload, material, lubrication, and the fastener standard still control the design.
Fine threads are more sensitive to damage, dirt, and pitch mismatch. A nut that starts on an M10 × 1.0 thread is not compatible with M10 × 1.5, even though both parts have the same nominal diameter. Start the nut by hand and stop if it binds before several turns.
How to measure metric thread pitch
- Clean the threads so dirt or burrs do not change the measurement.
- Measure the outside diameter across the thread crests with calipers. Compare the result with the nominal diameter; the measured value can be slightly below nominal because of tolerance and wear.
- Use a metric pitch gauge and find the leaf that seats against the thread without rocking or leaving visible gaps.
- If a pitch gauge is unavailable, measure the distance across several consecutive pitches and divide by the number of intervals. For example, five intervals measuring 7.5 mm indicate a 1.5 mm pitch.
- Confirm the complete designation against the mating part or its drawing. Diameter alone is not enough.
TPI conversion for comparison
The chart calculates the coarse-pitch TPI equivalent with TPI = 25.4 / pitch in mm. An M10 × 1.5 thread therefore has an equivalent of about 16.93 threads per inch. This number helps when comparing pitch spacing with an inch gauge, but it is not an inch-thread designation. Do not replace M10 × 1.5 with a nearby 5/8-16, 3/4-16, or other inch label.
Use the full designation when choosing a tap or hole
Thread pitch affects the tap drill, thread depth, clearance-hole choice, nut selection, and the correct replacement fastener. After identifying the thread, use a matching tap-drill recommendation for the tap type and material. A clearance hole is a separate design choice: it should pass the selected screw or bolt without assuming that the tapped-thread dimensions apply.
Related Mechanitec references
- Tap Drill Size Chart — Metric, UNC & UNF — choose a starting drill for a specified thread and tap process.
- Bolt Size to Wrench & Socket Size Chart — map a complete fastener designation to the applicable tool opening.
- How to Use Hole Wizard in SOLIDWORKS — create a matching modeled hole after the thread is identified.
Source note
The chart uses ISO 262:2023 for selected commercial fastener diameter-and-pitch combinations and ISO 261:1998 for the general metric-thread plan. The public Bossard technical reference is used as a representative engineering cross-check for ISO coarse and fine rows. Verify the current standard, fastener drawing, and supplier data for production-critical work.
Frequently asked questions
What is the coarse pitch for an M6 thread?
The preferred coarse pitch for M6 is 1.0 mm. The chart also lists M6 × 0.75 as a selected fine option.
What is the coarse pitch for an M10 thread?
The preferred coarse pitch for M10 is 1.5 mm. Selected fine options include 1.25 mm and 1.0 mm. Confirm the pitch before ordering a nut or tap.
Is M10 the same as M10 × 1.5?
M10 normally identifies the preferred coarse series, which is M10 × 1.5 in this chart. Use the complete M10 × 1.5 designation whenever a fine-pitch alternative is possible.
How do I convert metric pitch to TPI?
Divide 25.4 by the pitch in millimetres. For a 1.5 mm pitch, 25.4 ÷ 1.5 is about 16.93 TPI. Keep the original metric designation for the actual fastener.
Does a smaller pitch mean a stronger thread?
Not automatically. Fine and coarse threads behave differently, but the suitable choice depends on material, engagement, preload, joint design, and the applicable fastener standard.
