Metric Thread Pitch Chart with Inch Equivalents (M1–M100)

Published On: November 14, 2025|Categories: Fastener|

The table below lists ISO metric screw thread sizes from M1 up to M100. For each size it gives the standard coarse and fine thread pitches (in millimeters). The “Nearest Inch Thread Size” column shows the closest common Unified thread (UNC/UNF) nominal size for reference. If no direct UNC/UNF equivalent exists, it is marked “N/A”. (Fine-pitch variants are blank where none are defined.)

  • Metric Thread: Nominal diameter (M#) in millimeters.
  • Coarse/Fine Pitch: Standard ISO metric pitch in millimeters.
  • Inch Equivalent: Closest Unified nominal size (e.g. 1/4-20 UNC) or N/A if not standardized.
Metric Thread (mm) Coarse Pitch (mm) Fine Pitch (mm) Nearest Inch Thread Size
M1 0.25 0.20 N/A
M1.2 0.25 0.20 N/A
M1.4 0.30 0.20 N/A
M1.6 0.35 0.20 N/A
M1.7 0.35 — N/A
M1.8 0.35 0.20 N/A
M2 0.40 0.25 No. 1 (1-64 UNC)
M2.2 0.45 0.25 N/A
M2.3 0.40 — N/A
M2.5 0.45 0.35 No. 3 (3-48 UNC)
M2.6 0.45 — N/A
M3 0.50 0.35 No. 4 (4-40 UNC)
M3.5 0.60 0.35 No. 6 (6-32 UNC)
M4 0.70 0.50 No. 8 (8-32 UNC)
M5 0.80 0.50 No. 10 (10-24 UNC)
M6 1.00 0.75 1/4-20 UNC
M7 1.00 0.75 N/A
M8 1.25 1.00, 0.75 5/16-18 UNC
M9 1.25 1.00, 0.75 N/A
M10 1.50 1.25, 1.00, 0.75 3/8-16 UNC
M11 1.50 1.00, 0.75 N/A
M12 1.75 1.50, 1.25, 1.00 1/2-13 UNC
M14 2.00 1.50, 1.25, 1.00 9/16-12 UNC
M16 2.00 1.50, 1.00 5/8-11 UNC
M18 2.50 2.00, 1.50, 1.00 N/A
M20 2.50 2.00, 1.50, 1.00 3/4-10 UNC
M22 2.50 2.00, 1.50, 1.00 7/8-9 UNC
M24 3.00 2.00, 1.50, 1.00 1-8 UNC
M27 3.00 2.00, 1.50, 1.00 N/A
M30 3.50 3.00, 2.00, 1.50 1-1/8-7 UNC
M33 3.50 3.00, 2.00, 1.50 N/A
M36 4.00 3.00, 2.00, 1.50 1-3/8-6 UNC
M39 4.00 3.00, 2.00, 1.50 N/A
M42 4.50 4.00, 3.00, 2.00 N/A
M45 4.50 4.00, 3.00, 2.00 N/A
M48 5.00 4.00, 3.00, 2.00 N/A
M52 5.00 4.00, 3.00, 2.00 N/A
M56 5.50 4.00, 3.00, 2.00 N/A
M60 5.50 4.00, 3.00, 2.00 N/A
M64 6.00 4.00, 3.00, 2.00 N/A
M68 6.00 4.00, 3.00, 2.00 N/A
M72 6.00 4.00, 3.00, 2.00 N/A
M80 6.00 4.00, 3.00, 2.00 N/A
M90 6.00 4.00, 3.00, 2.00 N/A
M100 6.00 4.00, 3.00, 2.00 N/A

Note: Metric pitch values are per ISO metric thread standards. Inch-size equivalents are approximate nearest Unified sizes. Larger metric diameters (above ~36 mm) generally have no direct UNC/UNF counterpart, so these are marked N/A.

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