Bolt Tensile Stress Area (Metric)
Calculate the tensile stress area of a metric-thread bolt, A_t = (π/4)·(d − 0.9382·p)², from the nominal diameter d (mm) and the thread pitch p (mm). The tensile stress area is the EFFECTIVE cross-section resisting tension in a threaded bolt — and it is NOT the nominal-diameter area (the smooth cylinder) nor the root-diameter area (the thread bottom). Because of the helical thread geometry, tensile rupture occurs at an intermediate section, and tests showed it corresponds to an effective diameter equal to the average of the pitch and root diameters, leading to the formula with the 0.9382·p term (a geometric constant of the ISO metric thread, 60° triangular profile). The tensile area is the fundamental parameter for all bolt strength calculations: preload, tensile stress, proof load and ultimate strength are all found by multiplying A_t by the corresponding material stress. Using the wrong area (the larger nominal-diameter one) would overestimate strength and lead to undersized joints. Bolt tables list A_t for each diameter-pitch combination; this formula computes it for any metric thread. Enter the nominal diameter and the thread pitch.
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Bolt tensile stress area (metric)
The tensile stress area of a metric thread bolt is A_t = (π/4)·(d − 0.9382·p)², from the nominal diameter d and the thread pitch p. It is the effective cross section that carries tension in a threaded fastener — and it is not the area of the nominal diameter (that would be the plain shank) nor the area of the root diameter (the bottom of the thread). Because of the helical geometry of the thread, tensile fracture happens at an intermediate section, and testing showed that it matches an effective diameter equal to the mean of the pitch diameter and the root diameter, which leads to the formula with the 0.9382·p term (a geometric constant of the ISO metric thread, with its 60° triangular profile). The tensile stress area is the fundamental parameter behind every bolt strength calculation: preload, tensile stress, proof load and ultimate strength all come from multiplying A_t by the corresponding material stress. Using the wrong area (the larger nominal diameter one) would overestimate the strength and lead to undersized joints. Bolt tables list A_t for each diameter and pitch combination; this formula computes it for any metric thread (an M10 with 1.5 pitch, for example, gives A_t ≈ 58 mm²). Enter the nominal diameter and the thread pitch.
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The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.