Is ISMB 400 (Indian) equivalent to W16×50 (American)?
Steel Profiles
Close but not identical. ISMB 400: depth 400 mm, width 140 mm, weight 61.5 kg/m, Ix ≈ 20,220 cm⁴, Sx ≈ 1,011 cm³. W16×50 (American): depth ~413 mm (16.3″), width 180 mm (7.07″), weight ~74 kg/m, Ix ≈ 27,140 cm⁴, Sx ≈ 1,315 cm³. They are in the same general family (intermediate I-beams ~400 mm deep) but W16×50 is heavier and stiffer. A true ISMB 400 equivalent in AISC catalogs is closer to W16×40 (weight 60 kg/m, Sx ≈ 1,048 cm³). When substituting profiles across standards, always compare moment of inertia and section modulus — not just depth. CalcSteel lets you load any profile from any standard and compare their properties side by side.
Key takeaways
- ISMB 400 and W16×50 have similar depths (400 vs 414 mm) but W16×50 carries about 34% more strong-axis moment of inertia and 21% more steel per metre.
- The naming systems are built differently: an ISMB number is the actual depth in millimetres, while a W number is a nominal depth in inches paired with weight in pounds per foot.
- Section tables are standardized catalogs (IS 808 in India, the AISC Shapes Database in the US), each with its own rolling tolerances and flange geometry.
- By stiffness, ISMB 400 sits between W16×36 and W16×40, not at W16×50 — any real substitution must be re-verified against the governing code.
Full guide
ISMB 400 vs W16×50: Why They're Not Equivalent
Step-by-step with figures and sources — 9 min read
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