How to estimate the steel weight of a structure

October 9, 2026  ·  Indumor

Steel structures are largely priced by weight. Knowing how to estimate the kilos (or pounds) of your project lets you budget before detail engineering exists, and compare offers with judgment. At Indumor we do this takeoff daily; here is the short method.

1. Profiles weigh per meter

Every profile has a tabulated weight per meter: an IPN 200 runs ~26 kg/m, a UPN 100 ~10.6 kg/m, a 100x100x3 structural tube ~9 kg/m (roughly 17.5, 7.1 and 6 lb/ft). The takeoff is length × unit weight, summed.

2. Plate weighs by thickness

Golden rule: 1 mm of thickness = 7.85 kg/m² (steel plate ~40.8 lb/ft² per inch). A 3 mm sheet weighs ~23.6 kg/m²; 6 mm, ~47 kg/m². Multiply area by the factor and done.

3. The connections allowance

Gussets, base plates, bolts and stiffeners add 10–15% on top of the main members. For a quick estimate, take off the main members and add that percentage.

4. Useful orders of magnitude

• Light shed (purlins and trusses): 15–25 kg of steel per m² covered (3–5 lb/ft²).
• Industrial building with crane: 35–60+ kg/m², depending on span and load.
• Work platform: 60–120 kg/m² of platform, depending on load and flooring.

5. Why price per kilo is not the whole story

Two offers at the same $/kg can cost very differently: a poorly optimized structure weighs 20% more and you pay for all of it. And a kilo of plate girder is not worth the same as a kilo of purlin — it has more fabrication hours inside. That is why we quote with an open takeoff: you see the weights, the processes and where every number comes from.

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