What is the pitch of an M10 thread?

1.5 mm for the coarse thread. The fine pitches of M10 include 1.25 and 1 mm, written M10 × 1.25 and M10 × 1.

What is the pitch diameter of an M8 thread?

7.188 mm for the coarse thread M8 × 1.25, and 7.35 mm for the fine thread M8 × 1.

What does series 1, 2 and 3 mean?

It is the order of preference of ISO 261. Choose series 1 sizes first, series 2 if needed, and series 3 only when nothing else fits.

Metric thread chart: ISO coarse and fine pitch from M1 to M64

Every ISO metric thread from M1 to M64 in coarse and fine pitch, with the pitch diameter and the minor diameters of the bolt and the nut. Basic dimensions, the values a tolerance class is applied to.

Metric coarse thread chart

Thread	Ppitch, mm	d2 = D2pitch diameter, mm	d3bolt minor, mm	D1nut minor, mm	Series
M1	0.25	0.838	0.693	0.729	–
M1.1	0.25	0.938	0.793	0.829	–
M1.2	0.25	1.038	0.893	0.929	–
M1.6	0.35	1.373	1.171	1.221	1
M1.8	0.35	1.573	1.371	1.421	2
M2	0.4	1.74	1.509	1.567	1
M2.2	0.45	1.908	1.648	1.713	–
M2.5	0.45	2.208	1.948	2.013	1
M3	0.5	2.675	2.387	2.459	1
M3.5	0.6	3.11	2.764	2.85	2
M4	0.7	3.545	3.141	3.242	1
M4.5	0.75	4.013	3.58	3.688	–
M5	0.8	4.48	4.019	4.134	1
M6	1	5.35	4.773	4.917	1
M7	1	6.35	5.773	5.917	2
M8	1.25	7.188	6.466	6.647	1
M9	1.25	8.188	7.466	7.647	–
M10	1.5	9.026	8.16	8.376	1
M11	1.5	10.026	9.16	9.376	–
M12	1.75	10.863	9.853	10.106	1
M14	2	12.701	11.546	11.835	2
M16	2	14.701	13.546	13.835	1
M18	2.5	16.376	14.933	15.294	2
M20	2.5	18.376	16.933	17.294	1
M22	2.5	20.376	18.933	19.294	2
M24	3	22.051	20.319	20.752	1
M27	3	25.051	23.319	23.752	–
M30	3.5	27.727	25.706	26.211	1
M33	3.5	30.727	28.706	29.211	–
M36	4	33.402	31.093	31.67	1
M39	4	36.402	34.093	34.67	–
M42	4.5	39.077	36.479	37.129	1
M48	5	44.752	41.866	42.587	1
M52	5	48.752	45.866	46.587	–
M56	5.5	52.428	49.252	50.046	1
M60	5.5	56.428	53.252	54.046	2
M64	6	60.103	56.639	57.505	1

Metric fine thread chart

Thread	Ppitch, mm	d2 = D2pitch diameter, mm	d3bolt minor, mm	D1nut minor, mm
M1 × 0.2	0.2	0.87	0.755	0.783
M1.1 × 0.2	0.2	0.97	0.855	0.883
M1.2 × 0.2	0.2	1.07	0.955	0.983
M1.4 × 0.2	0.2	1.27	1.155	1.183
M1.6 × 0.2	0.2	1.47	1.355	1.383
M1.8 × 0.2	0.2	1.67	1.555	1.583
M2 × 0.25	0.25	1.838	1.693	1.729
M2.2 × 0.25	0.25	2.038	1.893	1.929
M2.5 × 0.35	0.35	2.273	2.071	2.121
M3 × 0.35	0.35	2.773	2.571	2.621
M3.5 × 0.35	0.35	3.273	3.071	3.121
M4 × 0.5	0.5	3.675	3.387	3.459
M4.5 × 0.5	0.5	4.175	3.887	3.959
M5 × 0.5	0.5	4.675	4.387	4.459
M5.5 × 0.5	0.5	5.175	4.887	4.959
M6 × 0.75	0.75	5.513	5.08	5.188
M7 × 0.75	0.75	6.513	6.08	6.188
M8 × 1	1	7.35	6.773	6.917
M8 × 0.75	0.75	7.513	7.08	7.188
M9 × 1	1	8.35	7.773	7.917
M9 × 0.75	0.75	8.513	8.08	8.188
M10 × 1.25	1.25	9.188	8.466	8.647
M10 × 1	1	9.35	8.773	8.917
M10 × 0.75	0.75	9.513	9.08	9.188
M11 × 1	1	10.35	9.773	9.917
M11 × 0.75	0.75	10.513	10.08	10.188
M12 × 1.5	1.5	11.026	10.16	10.376
M12 × 1.25	1.25	11.188	10.466	10.647
M12 × 1	1	11.35	10.773	10.917
M14 × 1.5	1.5	13.026	12.16	12.376
M14 × 1.25	1.25	13.188	12.466	12.647
M14 × 1	1	13.35	12.773	12.917
M15 × 1.5	1.5	14.026	13.16	13.376
M15 × 1	1	14.35	13.773	13.917
M16 × 1.5	1.5	15.026	14.16	14.376
M16 × 1	1	15.35	14.773	14.917
M17 × 1.5	1.5	16.026	15.16	15.376
M17 × 1	1	16.35	15.773	15.917
M18 × 2	2	16.701	15.546	15.835
M18 × 1.5	1.5	17.026	16.16	16.376
M18 × 1	1	17.35	16.773	16.917
M20 × 2	2	18.701	17.546	17.835
M20 × 1.5	1.5	19.026	18.16	18.376
M20 × 1	1	19.35	18.773	18.917
M22 × 2	2	20.701	19.546	19.835
M22 × 1.5	1.5	21.026	20.16	20.376
M22 × 1	1	21.35	20.773	20.917
M24 × 2	2	22.701	21.546	21.835
M24 × 1.5	1.5	23.026	22.16	22.376
M24 × 1	1	23.35	22.773	22.917
M25 × 2	2	23.701	22.546	22.835
M25 × 1.5	1.5	24.026	23.16	23.376
M25 × 1	1	24.35	23.773	23.917
M27 × 2	2	25.701	24.546	24.835
M27 × 1.5	1.5	26.026	25.16	25.376
M27 × 1	1	26.35	25.773	25.917
M28 × 2	2	26.701	25.546	25.835
M28 × 1.5	1.5	27.026	26.16	26.376
M28 × 1	1	27.35	26.773	26.917
M30 × 3	3	28.051	26.319	26.752
M30 × 2	2	28.701	27.546	27.835
M30 × 1.5	1.5	29.026	28.16	28.376
M30 × 1	1	29.35	28.773	28.917
M32 × 2	2	30.701	29.546	29.835
M32 × 1.5	1.5	31.026	30.16	30.376
M33 × 3	3	31.051	29.319	29.752
M33 × 2	2	31.701	30.546	30.835
M33 × 1.5	1.5	32.026	31.16	31.376
M35 × 1.5	1.5	34.026	33.16	33.376
M36 × 3	3	34.051	32.319	32.752
M36 × 2	2	34.701	33.546	33.835
M36 × 1.5	1.5	35.026	34.16	34.376
M39 × 3	3	37.051	35.319	35.752
M39 × 2	2	37.701	36.546	36.835
M39 × 1.5	1.5	38.026	37.16	37.376
M40 × 3	3	38.051	36.319	36.752
M40 × 2	2	38.701	37.546	37.835
M40 × 1.5	1.5	39.026	38.16	38.376
M42 × 4	4	39.402	37.093	37.67
M42 × 3	3	40.051	38.319	38.752
M42 × 2	2	40.701	39.546	39.835
M42 × 1.5	1.5	41.026	40.16	40.376
M45 × 4	4	42.402	40.093	40.67
M45 × 3	3	43.051	41.319	41.752
M45 × 2	2	43.701	42.546	42.835
M45 × 1.5	1.5	44.026	43.16	43.376
M48 × 4	4	45.402	43.093	43.67
M48 × 3	3	46.051	44.319	44.752
M48 × 2	2	46.701	45.546	45.835
M48 × 1.5	1.5	47.026	46.16	46.376
M50 × 3	3	48.051	46.319	46.752
M50 × 2	2	48.701	47.546	47.835
M50 × 1.5	1.5	49.026	48.16	48.376
M52 × 4	4	49.402	47.093	47.67
M52 × 3	3	50.051	48.319	48.752
M52 × 2	2	50.701	49.546	49.835
M52 × 1.5	1.5	51.026	50.16	50.376
M55 × 4	4	52.402	50.093	50.67
M55 × 3	3	53.051	51.319	51.752
M55 × 2	2	53.701	52.546	52.835
M55 × 1.5	1.5	54.026	53.16	53.376
M56 × 4	4	53.402	51.093	51.67
M56 × 3	3	54.051	52.319	52.752
M56 × 2	2	54.701	53.546	53.835
M56 × 1.5	1.5	55.026	54.16	54.376
M58 × 4	4	55.402	53.093	53.67
M58 × 3	3	56.051	54.319	54.752
M58 × 2	2	56.701	55.546	55.835
M58 × 1.5	1.5	57.026	56.16	56.376
M60 × 4	4	57.402	55.093	55.67
M60 × 3	3	58.051	56.319	56.752
M60 × 2	2	58.701	57.546	57.835
M60 × 1.5	1.5	59.026	58.16	58.376
M62 × 4	4	59.402	57.093	57.67
M62 × 3	3	60.051	58.319	58.752
M62 × 2	2	60.701	59.546	59.835
M62 × 1.5	1.5	61.026	60.16	60.376
M64 × 4	4	61.402	59.093	59.67
M64 × 3	3	62.051	60.319	60.752
M64 × 2	2	62.701	61.546	61.835
M64 × 1.5	1.5	63.026	62.16	62.376

Basic dimensions in millimetres. d2 and D1 are checked against two independent sources; d3 is calculated from the pitch with the ISO 724 formula. Series 1 is the first choice, then series 2.

Sources the values were checked against (5)

Metric thread pitch chart: coarse or fine

Every metric size has one coarse pitch and usually several fine ones. The coarse pitch is the default and is left out of the designation: M8 means M8 × 1.25. A fine pitch is always written, as in M8 × 1. Fine threads are used where the wall is thin, for fine adjustment, or where a smaller minor diameter would weaken the part; the coarse thread is the normal choice for bolts and nuts.

ISO metric thread dimensions: how they relate

All the diameters follow from the nominal size d and the pitch P with the formulas of ISO 724: the pitch diameter is d2 = d − 0.649519 P, the minor diameter of the nut is D1 = d − 1.082532 P and the minor diameter of the bolt is d3 = d − 1.226869 P. For M8 that gives 7.188, 6.647 and 6.466 mm. These are basic sizes: the actual limits of a bolt or a nut add the tolerance class, usually 6g for the bolt and 6H for the nut.

To cut the internal thread, the drill size is in the tap drill chart.

Metric threads: common questions

What is the pitch of an M10 thread?: 1.5 mm for the coarse thread. The fine pitches of M10 include 1.25 and 1 mm, written M10 × 1.25 and M10 × 1.
What is the pitch diameter of an M8 thread?: 7.188 mm for the coarse thread M8 × 1.25, and 7.35 mm for the fine thread M8 × 1.
What does series 1, 2 and 3 mean?: It is the order of preference of ISO 261. Choose series 1 sizes first, series 2 if needed, and series 3 only when nothing else fits.