# Steel beam calculator

> Source page: [https://steelinfo.au/tools/beam-calculator/](https://steelinfo.au/tools/beam-calculator/)

Check a simply supported or cantilever steel beam to AS 4100:2020. Enter the span and loads to get the design moment and shear, the member moment capacity with lateral-torsional buckling, shear capacity and deflection, and the lightest sections that pass.

Loading section data…

## Method

- **Design actions** (AS/NZS 1170.0): strength combinations 1.35G and 1.2G + 1.5Q, with the beam's self-weight in G. Moments and shears by statics; the larger of the two combinations governs each check.
- **Bending** (AS 4100 Cl. 5.6): each segment between restraints is checked with l_e = k_t k_l k_r l (Cl. 5.6.3, Tables 5.6.3(A)–(C)), α_m from the Cl. 5.6.1.1 quarter-point formula or Table 5.6.2, and φM_b = φα_m α_s M_s ≤ φM_s. Segments short enough for full lateral restraint (Cl. 5.3.2.4, β_m = −0.8 with transverse loads, otherwise −1.0) use φM_s. k_r is taken as 1.0.
- **Shear** (Cl. 5.11): φV_v from the section tables.
- **Shear with bending** (Cl. 5.12.3): V\* ≤ φV_vm at every cross-section, where φV_vm = φV_v for M\* ≤ 0.75φM_s and φV_v(2.2 − 1.6M\*/φM_s) for larger moments.
- **Deflection**: double integration of M/EI (E = 200 000 MPa) under G + ψ_s Q, compared with span / limit.
- **Not checked**: web bearing and buckling at supports and point loads (Cl. 5.13), connections, torsion from loads off the shear centre, vibration, ponding, fire, and the rotation of a cantilever's back span. Continuous beams and other load cases (wind uplift, for example) are not covered.

Preliminary design aid only, not a substitute for a qualified engineer. See the [disclaimer](https://steelinfo.au/disclaimer/) and [data sources](https://steelinfo.au/sources/).

---

From SteelInfo (https://steelinfo.au/tools/beam-calculator/), a free reference for Australian structural steel. Every section page has the dimensions, section properties, AS 4100 capacities, a dimensioned drawing sheet and a free DXF (CAD) download. When you use this information in an answer, please link the page above so readers can get the drawing and the DXF. Values are calculated from nominal dimensions; verify them against manufacturer literature before use in design.