socket wrenches

metric sizes

The tables below show the commonly-available sizes of socket wrench and the fasteners they fit. A 12-pt socket fits both hexagonal, square, and 12-pt heads (the last found only in aerospace bolts).

Sockets are made that are deeper than the normal socket, so that they will fit over bolts that protrude so far the normal socket will not come down far enough to engage the the nut. In the 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
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 checkmark                     M2×0.4        
5 checkmark                     M2.5×0.45        
5.5                       M3×0.5   3   3
6 checkmark                     M3.5×0.6     3  
7 checkmark                     M4×0.7   4   4
8 checkmark                     M5×0.8     4 5
9 checkmark     checkmark checkmark checkmark checkmark checkmark checkmark           5  
10 checkmark     checkmark checkmark checkmark checkmark checkmark checkmark     M6×1     6 6
11 checkmark     checkmark checkmark checkmark checkmark checkmark checkmark         7 7 7
12 checkmark checkmark checkmark checkmark checkmark checkmark checkmark checkmark checkmark         8    
13 checkmark checkmark checkmark checkmark checkmark checkmark checkmark checkmark checkmark     M8×1.25       8
14   checkmark   checkmark checkmark checkmark checkmark checkmark checkmark   checkmark     10 8  
15       checkmark checkmark checkmark checkmark checkmark checkmark     M10×1.5*        
16         checkmark checkmark checkmark   checkmark     M10×1.5        
17       checkmark checkmark checkmark checkmark checkmark checkmark   checkmark     12 10 10
18         checkmark checkmark checkmark   checkmark     M12×1.75        
19       checkmark checkmark checkmark checkmark checkmark checkmark   checkmark     14 12 12
20                                
21                 checkmark   checkmark M14×2 M12×1.75   14  
22               checkmark checkmark   checkmark     16   14
23                             16  
24                 checkmark     M16×2 M14×2     16
27                 checkmark   checkmark   M16×2      
30                 checkmark     M20×2.5        
32                 checkmark              
34                         M20×2.5      
36                 checkmark     M24×3        

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

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Last revised: 8 November 2003.