Structural Steel Section Properties Calculator

Structural Steel Section Properties Calculator helps you calculate geometric properties of various steel shapes — Rectangle, Circle, Rectangular Hollow Section (HSS), Pipe, and I-Beam — from their dimensions. Read about cross-sectional properties and understand how to calculate them.

About cross-sectional properties. Cross-sectional properties describe how a structural member resists axial, bending, and torsional loads. These properties depend entirely on the geometry (shape and size) of the section, not on the material. The most common geometric properties are cross-sectional area (A), second moments of area (Ix, Iy), and section moduli (Sx, Sy), which are used to calculate stresses and deflections.

About units. This calculator uses a single SI (metric) core for all calculations, and lets you view inputs and results in either metric or imperial units. Dimensions are entered in millimeters (mm) or inches (in). Results are shown as: area (cm² or in²), second moment of area (cm⁴ or in⁴), and section modulus (cm³ or in³). For I-Beam shapes, additional properties — torsion constant (J, in cm⁴ or in⁴) and warping constant (Cw, in cm⁶ or in⁶) — are also provided.

About shape types. The tool supports five section shapes:

• Rectangle: solid rectangular bar
• Circle: solid round bar
• Rectangular Hollow (HSS): thin-walled hollow rectangular tube
• Pipe: thin-walled hollow round tube
• I-Beam: wide flange section with flanges and a central web

You can switch between shapes using the shape selector, only the relevant inputs will be active at any time.

Calculation. This calculator computes the section properties directly from user-entered geometric dimensions using standard engineering formulas. All dimensions are converted to meters internally, for consistent results across metric and imperial systems.

Formulas:

• Rectangle
  • A = b·h (cross-sectional area)
  • I_x = b·h³ / 12 (moment of inertia about x-axis)
  • I_y = h·b³ / 12 (moment of inertia about y-axis)
  • S_x = I_x / (h/2), S_y = I_y / (b/2) (section moduli)
• Circle
  • A = π·d² / 4
  • I = π·d⁴ / 64 (same for x and y)
  • S = I / (d/2)
• Rectangular Hollow Section (HSS)
  • A = b·h − (b−2t)·(h−2t)
  • I_x = [b·h³ − (b−2t)·(h−2t)³] / 12
  • I_y = [h·b³ − (h−2t)·(b−2t)³] / 12
  • S_x = I_x / (h/2), S_y = I_y / (b/2)
• Pipe
  • A = π·(D_o² − D_i²) / 4
  • I = π·(D_o⁴ − D_i⁴) / 64
  • S = I / (D_o/2)
• I-Beam
  • A = 2·b_f·t_f + (d − 2·t_f)·t_w + 2·r²·(π/4 − 1)
  • I_x = [b_f·d³ − (b_f−t_w)·(d−2·t_f)³] / 12
  • I_y = [2·t_f·b_f³ + (d−2·t_f)·t_w³] / 12
  • S_x = I_x / (d/2), S_y = I_y / (b_f/2)
  • J = [2·b_f·t_f³ + (d−2·t_f)·t_w³] / 3 (torsion constant)
  • C_w = b_f·d²·t_f³ / 24 (warping constant)

Examples:

• Example 1 — Rectangle: b = 200 mm, h = 300 mm → A = 60000 mm² = 600 cm² → I_x = 4.5·10⁷ mm⁴ = 4500 cm⁴
• Example 2 — Circle: d = 200 mm → A = 31416 mm² = 314 cm² → I = 7.85·10⁶ mm⁴ = 785 cm⁴
• Example 3 — Pipe: D_o = 219.1 mm, D_i = 200.1 mm → A ≈ 6172 mm² = 61.7 cm² → I ≈ 8.78·10⁶ mm⁴ = 878 cm⁴

Corresponding tools.To calculate the weight of a steel section from its area, use the Steel Weight Calculator. To convert between metric and imperial length units, use the Length Units Converter.