Bolt Selection Calculator Online (Find Size and Grade from Load)

bolt Selection Calculator (Find Size and Grade from Load)

The most common reverse question in bolt sizing: the joint must carry 10 kN - which size and grade do you need? This online calculator works backwards from the working load, load type and safety factor to the smallest size x grade combination that satisfies the requirement, with a "grade 8.8 minimum" recommendation since grade 8.8 is the most widely stocked, best-value choice.

Allowable load equals sigma_s x As divided by the safety factor for tension, and about 0.6σb on the shank area for shear. The calculator scans M6 through M30 and grades 4.8 to 12.9 and returns the first combination meeting the requirement. Take SF = 1.5 for static, 2 for general duty, 2.5 for dynamic and 3 for impact or critical joints.

For shear, prefer fitted bolts with unthreaded shank in reamed holes; with weak parent material (aluminum, plastic), increasing the size beats increasing the grade. Use our full selection tool and preload calculator for detailed checks. Zhuhai Jiali Hardware supplies grade 4.8-12.9 and stainless precision screws - contact us for quotes.