Metric Bolt Size, Strength & Torque
Look up the pitch, stress area, proof and tensile load and recommended tightening torque for metric bolts by size and grade, free online.
About this calculator
Metric coarse-thread data (ISO 898-1): tensile stress area A_s and strength grades 4.6, 8.8, 10.9, 12.9. Proof load = A_s × proof stress; tensile load = A_s × tensile strength. Tightening torque T ≈ K·d·F with K ≈ 0.2 (dry, plain) at 75% of proof load for a reusable joint. Tap drill ≈ nominal diameter − pitch.