Section properties calculator
Enter a profile's dimensions and get its exact section properties: area A, second moments of area Ix and Iy, elastic section moduli Sx and Sy, radii of gyration, torsion constant J, and mass per metre. Every value is integrated straight from the section polygon with Green's theorem — the same math a structural engineer uses — so there is no estimation error.
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 | 3800 | mm² |
| Mass / metre | m | 7.220(4.852 lb/ft) | kg/m |
| 2nd moment | Ix | 2.293e+7 | mm⁴ |
| 2nd moment | Iy | 1.682e+6 | mm⁴ |
| Section mod. | Sx | 229267 | mm³ |
| Section mod. | Sy | 33633 | mm³ |
| Gyration | rx | 77.67 | mm |
| Gyration | ry | 21.04 | mm |
| Torsion | J | 126667 | mm⁴ |
| Published catalogue weight: 5.80 kg/m · computed Δ 24% | |||
Derived exactly from the section polygon (Green’s theorem). Fillets excluded (<2% effect). Verify against certified data before release.
How the properties are calculated
Straight-sided sections (I-beams, channels, angles, hollow sections, flats, T-slots) are integrated exactly from their polygon outline; round sections use closed-form circle formulas. The centroid is located first, then all second moments are referred to the centroidal axes by the parallel-axis theorem. Weight per metre comes from area multiplied by the chosen material density — 1.9 g/cm³ for E-glass FRP, 2.7 for aluminium, 7.85 for steel.
Why deterministic geometry matters
A profile is a constant cross-section swept along a straight axis, so its stiffness and weight are pure functions of that 2-D shape. Nothing is simulated or guessed. Change one dimension and every property updates in lock-step — which is exactly why the render and the datasheet can never disagree with each other.
What to verify before you rely on it
Root fillets are ignored (a conservative sub-2% effect on most sections) and angles report properties about their geometric axes rather than principal axes. For a final design submission, always cross-check against your certified test data. Dimviz is built to get you a trustworthy first number in seconds, not to replace a stamped calculation.
FAQ
What section properties does it calculate?+
Area (A), centroid, second moments of area (Ix, Iy), elastic section moduli (Sx, Sy), radii of gyration (rx, ry), torsion constant (J) and mass per metre from material density.
Is it accurate for FRP and aluminium profiles?+
Yes. The geometry math is material-independent; only density and modulus change per material. Pick FRP, aluminium, steel or PU-FRP window and the weight and stiffness update accordingly.
Can I calculate a custom section?+
The tool covers I-beam, channel, angle, square and rectangular hollow, round tube, round rod, flat bar and T-slot. Fully arbitrary polygons (e.g. multi-cavity window frames) are on the roadmap via DXF import.