Technical Tables & Calculators

Wrench Size Chart (Jaw Size) vs. Bolt Size

Choosing a wrench that fits the nut or bolt head correctly helps prevent rounding off the head and makes the job safer. This table shows the wrench jaw size (mm) used with each size of hex-head bolt by standard — for example, M8 uses a 13 mm wrench, M10 uses 17 mm, M12 uses 19 mm, and M16 uses 24 mm. The wrench jaw size equals the across-flats width (S) of that bolt's head.

Samakkee Salukpan supplies hex-head nuts and bolts in every grade and size, with expert guidance to help you choose the right fit for your job site.