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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 can easily occur.

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.

30

100

60

30

80

80

30

.
Allen Wrench Conversion Table -
Hex Key Equivalent Sizes
Difference in 1/1000s of an inch
Size in Inches
Standard
SAE
Hex Key
Sizes

(inches)
Metric
Hex Key Sizes

(mm)

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

-

-

15-key set
8-key set in yellow
15-key set

-

-

0.02756

0.7

Interchangable

0
0.028
0.028

7
0.035
0.035

Interchangable - -
1mm= 0.03937"

0
0.03543

0.9
4
0.03937

1.0

Also a standard size

10

0.04921

1.25

Also a standard size

1
0.050
0.050

Interchangable

1
0.05118

1.3
8
0.05905

1.5

-

3
0.06250
1/16

too small

16

0.07813
5/64

too big

1
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

1
0.15748

 

4

20

0.17716

4.5

-

10
0.18750
3/16

 

-

9
0.19685

 

5

-

19

0.21653

5.5

-

3
0.219
7/32

 

-

16

0.23622

 

6

-

16

0.250
1/4

 

-

25

0.27559

 

7

-

32

0.3125
5/16

 

-

2
0.31496

 

8

40

0.35433

 

9

Also a standard size

21

0.375
3/8

 

-

19

0.39370

 

10

 1cm= 0.39370"

Metric Set from Amazon -
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 Set from Amazon -
.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

.
Larger Sizes

27
0.406
13/32

 

 -

4

0.433

11

Close enough (7/16 and 11mm)

31
0.438
7/16

 

4

0.469
15/32

 

Close enough (15/32 and 12mm)

28
0.472

 

12
12
0.500

1/2

 

 -

19
0.512

 

13

 -

20
0.531
17/32

 

 -

11
0.551

 

14

 -

28
0.563
9/16

 

 -

3

0.591

 

15

Close enough (19/32 and 15mm)

31
0.594
19/32

 Bicycle

5
0.625

5/8

 

?

26
0.630

 Bicycle

16

-

13
0.656
21/32

 

 -

18
0.669

 

17

 -

21
0.688
11/16

 

 -

10
0.709

 

18

 -

29
0.719
23/32

 

 -

2

0.748

 

19

Close enough (3/4 and 19mm)

31
0.750

3/4

 

6
0.781
25/32

 

 -

25
0.787

 

20

 -

14
0.813
13/16

 

 -

17
0.827

 

21

 -

22
0.844
27/32

 

 -

9
0.866

 

22

 -

11
0.875
7/8

 

 -

1

0.9055

 

none

Close enough (29/32 and 23mm)

31
0.9063
29/32

 

7
0.938
15/16

 

 -

55

0.945

 

24

 -

39

0.984

25

-

16

1.000
1

 -

  1"= 2.54cm (= 0.254m)

63

1.063

27

-

118

1.181

30

-

79

1.260

32

-

157

1.417

36

-

236

1.653

42

-

158

1.811

46

-

70

70

70

70

170 - 450

CONVERSION FACTORS

English to Metric

1 inch =

 

2.54 centimeters (= 0.254m)

Metric to English

1 centimeter =

 

0.3937 inches


Many thanks to Bob V. for the dimension 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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©2011 Vaughn Aubuchon
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This Vaughns Allen Wrench Size Equivalence Chart
was last updated on 2014-04-07.