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SAE-Metric Allen Wrenches

Allen Wrench
(Hex Key) Conversion

Size Equivalence Chart
by Vaughn Aubuchon

This Allen wrench size conversion chart converts metric-sized wrenches to standard-sized wrenches, and shows which wrenches are roughly interchangeable. Not using the exact size hex key is NOT ADVISED, because stripping (rounding) of the socket can easily occur. You don't want your hex key to change from a wrench into a drill.
.

-

Metric wrench sizes are shown, along with their "English Standard" equivalence, in 1/1000s of an inch. "Standard-size" wrenches refers to SAE sizes - the Society of Automotive Engineers.

Conversion Factors
.



     Allen Wrench
     Conversion Table -

       Hex Key Equivalent Sizes

Differ-ence in 1/1000s of an inch
Size
in
Inches
Stan-dard
SAE
Hex Key
Sizes

(inches)
Metric
Hex Key Sizes

(mm)

Notes - compares Standard and Metric Allen wrench sizes (where they CLOSELY match, and where they don't - wrench equivalence)

-

-

15-key set
15-key set

-

-

0.02756

0.7

Interchangable
0.028" and 0.7mm

0.44

0.02800
0.028

7
0.03500
0.035

Interchangable
0.035" and 0.9mm

0.43

0.03543

0.9
4
0.03937

1.0

Also a standard size

10
0.04921

1.25

Also a standard size

1
0.05000
0.050

Interchangable
0.05" and 1.3mm

1.18

0.05118

1.3
8
0.05905

1.5

-

3
0.06250
1/16

-

16

0.07813
5/64

Interchangable
5/64" and 2mm

0.61

0.07874

2

15

0.09375
3/32

-

5
0.09842

2.5

-

11
0.10937
7/64

-

9
0.11811

3

-

7
0.12500
1/8

-

12
0.13779

3.5

Also a standard size

3
0.14062
9/64

-

16

0.15625
5/32

 

Interchangable
5/32" and 4mm

1.23

0.15748

 

4

20

0.17716

4.5

-

10
0.18750
3/16

 

-

9
0.19685

 

5

-

19

0.21653

5.5

-

3
0.21875
7/32

 

-

16

0.23622

 

6

-

16

0.25000
1/4

 

-

25

0.27559

 

7

-

32

0.31250
5/16

 

Interchangable
5/16" and 8mm

2.46

0.31496

 

8

40

0.35433

 

9

Also a standard size

21

0.37500
3/8

 

-

19

0.39370

 

10

 1cm= 0.39370"

.
Metric Allen Set (Amazon) (15 pieces) -
0.7mm, 0.9mm, 1.3mm, 1.5mm, 2.0mm, 2.5mm, 3.0mm
4.0mm, 4.5mm, 5.0mm, 5.5mm, 6.0mm, 7.0mm, 8.0mm, 10.0mm

SAE Allen Set (Amazon) (15 pieces) -
.028",.035",.050", 1/16", 5/64", 3/32", 7/64",
1/8", 9/64", 5/32", 3/16", 7/32", 1/4", 5/16", and 3/8"

All the wrench sizes above were taken from Wikipedia at -
Hex Key - Wikipedia
.

-

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     Larger
     Allen Driver Sizes

Differ-ence in 1/1000s of an inch
Size
in
Inches
Stan-dard
SAE
Hex Key
Sizes

(inches)
Metric
Hex Key Sizes

(mm)

Notes - compares Standard and Metric Allen wrench sizes (where they CLOSELY match, and where they don't - wrench equivalence)

27
0.40625
13/32

 

 -

4.43

0.43307

11

Close -
7/16" and 11mm

31
0.43750
7/16

 

3.69

0.46875
15/32

 

Close -
15/32" and 12mm

28
0.47244

 

12
12
0.50000
1/2

 

 -

19
0.51181

 

13

 -

20
0.53125
17/32

 

 -

11
0.55118

 

14

 -

28
0.56250
9/16

 

 -

3.2

0.59055

 

15

Close enough
19/32" & 15mm

31
0.59375
19/32

 Bicycle

5
0.62500
5/8

 

?

26
0.62992

 Bicycle

16

-

13
0.65625
21/32

 

 -

18
0.66929

 

17

 -

21
0.68750
11/16

 

 -

10
0.70866

 

18

 -

29
0.71875
23/32

 

 -

1.97

0.74803

 

19

Close enough
3/4" and 19mm

31
0.75000
3/4

 

6
0.78125
25/32

 

 -

25
0.78740

 

20

 -

14
0.81250
13/16

 

 -

17
0.82677

 

21

 -

22
0.84375
27/32

 

 -

9
0.86614

 

22

 -

11
0.87500
7/8

 

 -

0.74

0.90551

 

none

Close enough
29/32" & 23mm

31
0.90625
29/32

 

7
0.93750
15/16

 

 -

55

0.94488

 

24

 -

39

0.98425

25

-

16

1.0000
1

 -

  1"= 2.54cm
(= 0.254m)

63

1.06299

27

-

118

1.18110

30

-

79

1.25984

32

-

157

1.41732

36

-

236

1.65354

42

-

158

1.81102

46

-

60

90

60

50

180 - 450



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 Conversion Factors
English
to
Metric
English

 Metric

-

1 inch =
1 inch =
1 inch =

2.54 centimeters
25.4 mm
0.0254 meters

1 foot =

30.48 cm

-

Metric
to
English
Metric

 English

-

1 mm =

0.03937 inches

1 cm =

0.3937 inches

1 meter =

39.37 inches

90

110

190 - 450

20



.
 SAE Wrench Conversion

Many thanks to Johnny S. for the fix (2020-01-25)

Many thanks to Isiah L. for the fix (2019-12-22).

Many thanks to Bob V. for the fix (2013-12-04).


DISCLAIMER:
Although the author has tried to be as accurate as possible, errors are possible.

I could not find an online table like the above. So, I made this conversion chart, to help myself understand the relationships between wrench sizes of the metric system and wrench sizes of the standard system. I hope that it helps you.

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This Vaughns Allen Wrench Size Equivalence
Chart was last updated on 2020-06-12.