Machine Screw Size Charts and Conversion Tables (2024)

A #8 screw size is .164 fraction of an inch. The diameters listed in the chart below are in fractions of an inch, so the #12 is just shy of 1/4 inch.

A more detailed table with thread count can be found below, along with tap drill sizes.
Detailed screw sizes charts.
Screw and Tap Drill sizes

Machine Screw Sizes

Decimal and Millimeter Equivalents of Fractional Parts of an Inch

Fraction	Decimal	Millimeter	Fraction	Decimal	Millimeter	Fraction	Decimal	Millimeter
1	1.0000	25.4000	21/32	0.6562	16.6687	5/16	0.3125	7.9375
63/64	0.984	25.0031	41/64	0.6406	16.2719	19/64	0.2969	7.5406
31/32	0.9688	24.6062	5/8	0.6250	15.8750	9/32	0.2812	7.1437
61/64	0.9531	24.2094	39/64	0.6094	15.4781	17/64	0.2656	6.7469
15/16	0.9375	23.8125	19/32	0.5938	15.0813	1/4	0.2500	6.3500
59/64	0.9219	23.4156	37/64	0.5781	14.6844	15/64	0.2344	5.9531
29/32	0.9062	23.0187	9/16	0.5625	14.2875	7/32	0.2188	5.5563
57/64	0.8906	22.6219	35/64	0.5469	13.8906	13/64	0.2031	5.1594
7/8	0.8750	22.2250	17/32	0.5312	13.4937	3/16	0.1875	4.7625
55/64	0.8594	21.8281	33/64	0.5156	13.0969	11/64	0.1719	4.3656
27/32	0.8438	21.4312	1/2	0.5000	12.7000	5/32	0.1562	3.9688
53/64	0.8281	21.0344	31/64	0.4844	12.3031	9/64	0.1406	3.5719
13/16	0.8125	20.6375	15/32	0.4688	11.9062	1/8	0.1250	3.1750
51/64	0.7969	20.2406	29/64	0.4531	11.5094	7/64	0.1094	2.7781
25/32	0.7812	19.8438	7/16	0.4375	11.1125	3/32	0.0938	2.3812
49/64	0.7656	19.4469	27/64	0.4220	10.7188	5/64	0.0781	1.9844
3/4	0.7500	19.0500	13/32	0.4062	10.3187	1/16	0.0625	1.5875
47/64	0.7344	18.6531	25/64	0.3906	9.9219	3/64	0.0469	1.1906
23/32	0.7188	18.2563	3/8	0.3750	9.5250	1/32	0.0312	0.7937
45/64	0.7031	17.8594	23/64	0.3594	9.1281	1/64	0.0156	0.3969
11/16	0.6875	17.4625	11/32	0.3438	8.7312	--	--	--
43/64	0.6719	17.0656	21/64	0.3281	8.3344	--	--	--

Version 3.7.8

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