Section modulus calculator
Calculate the elastic section modulus (Sx, Sy) of any beam or profile from its dimensions. Section modulus S = I / c ties directly to bending stress, so it's the number you check against allowable stress. Pick a shape or import a DXF, and Dimviz computes Sx and Sy exactly from the section, alongside moments of inertia, radii of gyration and weight per metre.
DXF (LWPOLYLINE/CIRCLE) · CSV/XLSX with X,Y columns (blank row = new loop). DWG → export as DXF first.
EL 23,000 MPa · Pultruded FRP (E-glass / polyester)
| Area | A | 5472 | mm² |
| Mass / metre | m | 10.397(6.986 lb/ft) | kg/m |
| 2nd moment | Ix | 4.754e+7 | mm⁴ |
| 2nd moment | Iy | 3.487e+6 | mm⁴ |
| Section mod. | Sx | 396173 | mm³ |
| Section mod. | Sy | 58118 | mm³ |
| Gyration | rx | 93.21 | mm |
| Gyration | ry | 25.24 | mm |
| Torsion | J | 262656 | mm⁴ |
| Published catalogue weight: 8.40 kg/m · computed Δ 24% | |||
Derived exactly from the section polygon (Green’s theorem). Fillets excluded (<2% effect). Verify against certified data before release.
Why section modulus matters
Bending stress σ = M / S, so for a given moment M, a larger section modulus means lower stress. It's the property you size beams by. Dimviz reports Sx (strong axis) and Sy (weak axis) as I divided by the distance to the extreme fibre — exact for your geometry, no table interpolation.
Elastic section modulus, computed live
Every value comes from the section polygon, so a change to any dimension instantly updates Sx and Sy. That makes it fast to size a member or compare candidate profiles against a required section modulus.
FAQ
How do you calculate section modulus?+
Section modulus S = I / c, where I is the second moment of area and c is the distance from the centroid to the extreme fibre. Dimviz computes I and c from the geometry and returns Sx and Sy.
Elastic or plastic section modulus?+
Dimviz reports the elastic section modulus (used with allowable-stress and elastic design). Plastic section modulus is on the roadmap.
How is it different from moment of inertia?+
Moment of inertia (I) is about resistance to bending curvature; section modulus (S = I/c) relates moment to peak stress. Dimviz shows both.