The cross-sectional area of a beam or bar sets its weight per metre, its axial strength (stress = force ÷ area) and how much material it uses. It is the first number an engineer needs when choosing a steel profile or timber.
How to use the Cross-Sectional Area Calculator
- Profile
- Width W
- Height H
- Thickness t (wall or flange)
- Web thickness t_w
- Outer diameter D
Results update as you type, and everything is calculated in your browser.
How it works
Choose the profile. W is the overall width (flange width), H the overall height, t the wall or flange thickness and t_w the web thickness. Multiply the area by the length and density to get the weight.
Inputs explained
| Field | What to enter |
|---|---|
| Profile | Choose one: Rectangle, Hollow rectangle, I-beam, C-channel … |
| Width W | Units: cm, m, mm, in, ft, yd … |
| Height H | Units: cm, m, mm, in, ft, yd … |
| Thickness t (wall or flange) | Units: cm, m, mm, in, ft, yd … |
| Web thickness t_w | Units: cm, m, mm, in, ft, yd … |
| Outer diameter D | Units: cm, m, mm, in, ft, yd … |
Example values
How the main result changes when Width W changes and everything else stays at the example values above:
| Width W (cm) | Cross-sectional area (cm²) |
|---|---|
| 5 | 26.08 |
| 7.5 | 32.08 |
| 10 | 38.08 |
| 12.5 | 44.08 |
| 15 | 50.08 |
| 20 | 62.08 |
Formula
Rectangle W·H · Hollow rectangle W·H − (W − 2t)(H − 2t) · I-beam / C-channel 2W·t + (H − 2t)·t_w
T-section W·t + (H − t)·t_w · L-angle W·t + (H − t)·t_w · Tube π(D² − (D − 2t)²)/4
Worked example
Inputs — Profile: I-beam; Width W: 10 cm; Height H: 20 cm; Thickness t (wall or flange): 1.2 cm; Web thickness t_w: 0.8 cm.
Results — Cross-sectional area = 38.08 cm².
Key terms
- Flange
- The horizontal plate of an I, C or T profile.
- Web
- The vertical plate connecting the flanges.
Frequently asked questions
Why does cross-sectional area matter?
Stress equals force divided by area, and weight equals area × length × density.
Is a bigger area always stronger in bending?
Not necessarily – bending depends on the moment of inertia, i.e. how far material is from the axis.
How do I get the weight of a steel beam?
Area × length × 7,850 kg/m³.
What is the web of a beam?
The vertical plate joining the flanges.