US Bolt Head/Wrench Size Table

Bolt
Diameter

Head/Wrench Size

Hex Bolt
-
Lag Bolt
-
Square Bolt

Heavy Hex Bolt

#6

1/4

-

#8

1/4

-

#10

5/16

-

#12

5/16

-

1/4

7/16 or 3/8

-

5/16

1/2

-

3/8

9/16

-

7/16

5/8

-

1/2

3/4

7/8

9/16

13/16

-

5/8

15/16

1-1/16

3/4

1-1/8

1-1/4

7/8

1-5/16

1-7/16

1

1-1/2

1-5/8

1-1/8

1-11/16

1-3/4

1-1/4

1-7/8

2