Metric Bolt Heads and Wrench Sizes

ANSI/ISO, DIN and JIS metric bolt head and wrench sizes reference table. Includes spanner/wrench sizes and Allen key dimensions for metric bolts.

ISO Metric Threaded Bolt (mm)	ANSI/ISO Spanner Size (mm)	DIN Spanner Size (mm)	JIS Spanner Size (mm)	ANSI/ISO Allen Key (mm)
3	5.5
4	7	7	7
5	8	8	8	4
6	10	10	10	5
7		11
8	13	13	12	6
10	15, 16	17	14	8
12	18	19	17	10
14	21	22	19
16	24	24	22	14
18		27
20	30	30		17
24	36			19