18mm → 11/16" Imperial
The nearest imperial equivalent of 18mm is 11/16" (0.54mm difference).
A 18mm socket or wrench is closest to 11/16" imperial (17.46mm), a difference of 0.54mm. The gap is significant — using the imperial size risks rounding the fastener. Use the correct metric socket.
The 0.54mm difference may cause the socket to slip or round the fastener head. Use the correct metric size whenever possible.
Related Sizes
About 18mm Conversion
A 18mm metric socket or wrench is closest to 11/16" imperial (17.46mm), with a difference of 0.54mm. The gap between sizes is significant — using the imperial substitute risks rounding the fastener head. Always use the correct metric socket. The second-nearest imperial size is 3/4" (19.05mm, 1.05mm off). Automotive and industrial. When working on mixed metric and imperial fasteners, a combination socket set covers both systems and eliminates guesswork.