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socket wrenches
metric sizes

The tables below show the commonly-available sizes of metric socket wrenches and the fasteners they fit. A 12-pt socket fits both hexagonal, square (sort of), and 12-pt heads (the last found mainly in aerospace bolts, but also on automobile engines as, for example, head bolts).

Sockets are made that are deeper than the normal socket, so that they will fit over bolts that protrude so far that a normal socket will not come down far enough to engage the nut. In the column headings, these are indicated by a “d”.

One end of a socket has a square recess which fits the socket wrench. In consumer wrenches, the square drives are ¼″, 3/8″, ½″, and ¾″.

American Socket Wrenches: Metric Sizes to 36mm
Size (mm)	¼″ drive			3/8″ drive				½″ drive				Fits bolt or nut with this diameter
Size (mm)	6 pt	12 pt	6pt d	6 pt	12 pt	6pt d	12pt d	6 pt	12 pt	6pt d	12 d	ANSI cap screws, formed hex screws, standard metric	ANSI heavy hex	ISO	J.I.S. (Japan)	D.I.N (Germany)
3
4	✓											M2 × 0.4
5	✓											M2.5 × 0.45
5.5												M3 × 0.5		3		3
6	✓											M3.5 × 0.6			3
7	✓											M4 × 0.7		4		4
8	✓											M5 × 0.8			4	5
9	✓			✓		✓	✓	✓	✓						5
10	✓			✓	✓	✓	✓	✓	✓			M6 × 1			6	6
11	✓			✓	✓	✓	✓	✓	✓					7	7	7
12	✓	✓	✓	✓	✓	✓	✓	✓	✓					8
13	✓	✓	✓	✓	✓	✓	✓	✓	✓			M8 × 1.25				8
14		✓		✓	✓	✓	✓	✓	✓		✓			10	8
15				✓	✓	✓	✓	✓	✓			M10 × 1.5*
16					✓	✓	✓		✓			M10 × 1.5
17				✓	✓	✓	✓	✓	✓		✓			12	10	10
18					✓	✓	✓		✓			M12 × 1.75
19				✓	✓	✓	✓	✓	✓		✓			14	12	12
20
21									✓		✓	M14 × 2	M12 × 1.75		14
22								✓	✓		✓			16		14
23															16
24									✓			M16 × 2	M14 × 2			16
27									✓		✓		M16 × 2
30									✓			M20 × 2.5
32									✓
34													M20 × 2.5
36									✓			M24 × 3

* Produced in the US, but not an ISO size. The 16mm between flats should be used instead.

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socket wrenches metric sizes

socket wrenches
metric sizes