What wrench fits a M16 bolt?

Across-flats wrench/socket size by head type - a flange bolt often uses a smaller wrench than a standard hex bolt of the same diameter, so always check the head type.

System

Bolt size

Nominal diameter	16 mm
Standard hex	24 mm
Hex flange	22 mm
Recommended clearance hole (medium fit)	17.5 mm
≈	≈ 15/16" (5/8")

Reference values only - always verify against the actual part before machining, tapping or tightening anything.