Steel Beam RSJ Calculator — UDL, Moment & Beam Selection
Calculate UDL from floor loading, bending moment and select a suitable S275 steel beam from moment capacity tables.
Clear span between supports
Width of floor supported by beam
How We Calculate This
This calculator determines the required steel beam size by calculating the bending moment from floor loading and selecting a suitable Universal Beam section.
Load calculation
UDL (kN/m) = (Dead Load × 1.35 + Imposed Load × 1.5) × Floor Width
Bending Moment M = wL² / 8 (kNm)
For simply supported beams with uniformly distributed loading.
Beam selection
The smallest S275 Universal Beam with a moment capacity exceeding the calculated bending moment is suggested. This is indicative only — a structural engineer must verify for deflection, shear, LTB and connections.
Frequently Asked Questions
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Last updated: March 2026
All calculations are estimates. Verify with your supplier.