| Beam case | Span | E | I | Load | Typical use |
|---|---|---|---|---|---|
| Simply supported, center load | 6.0 m | 200 GPa | 5.40 × 109 mm⁴ | 25 kN | Steel floor beam check |
| Simply supported, UDL | 5.0 m | 11 GPa | 1.82 × 109 mm⁴ | 8 kN/m | Timber joist screening |
| Cantilever, end load | 2.4 m | 200 GPa | 8.90 × 108 mm⁴ | 6 kN | Canopy bracket estimate |
| Fixed-fixed, UDL | 4.8 m | 30 GPa | 3.10 × 109 mm⁴ | 12 kN/m | Concrete transfer strip |
- Choose the beam case that best matches the real support and load arrangement.
- Enter span length and select the correct length unit.
- Enter the material elastic modulus using GPa, MPa, or Pa.
- Choose a section mode, then either enter dimensions or provide moment of inertia directly.
- Enter the point load or distributed load using the matching unit.
- Press the calculate button to show stiffness, deflection, rigidity, and the graph above the form.
- Use the CSV or PDF buttons to save the result summary for review or sharing.
- Check the span-deflection screen, then verify final design decisions against your governing code and a qualified engineer.
1. What does beam stiffness mean?
Beam stiffness describes how strongly a member resists bending under load. Higher stiffness means less deflection for the same span, support condition, material, and section geometry.
2. Why is EI important?
EI combines material stiffness and section geometry into one value. A larger elastic modulus or a larger moment of inertia increases flexural rigidity and reduces beam deflection.
3. Why do support conditions change the answer so much?
Restraint changes the beam curvature pattern. A fixed-fixed beam usually deflects much less than a simply supported beam, while a cantilever is often the most flexible case.
4. Can I use this for steel, timber, or concrete members?
Yes. Enter the correct elastic modulus and a realistic section moment of inertia. The calculator then applies the selected beam formula using consistent units.
5. For a distributed load, what load value should I enter?
Enter the load intensity per unit length, such as kN/m. The calculator internally converts it to total load where needed for equivalent stiffness output.
6. What if I already know the moment of inertia?
Use the direct inertia mode. That is useful when you already have section properties from a catalog, software model, or manufacturer table.
7. Is the L/360 result enough for final design?
No. It is only a quick screen. Final design should also check bending, shear, vibration, local stability, creep, connection behavior, and your governing code requirements.
8. Can this replace a full structural analysis?
No. It is best for fast preliminary checks and education. Complex framing, multiple spans, unusual loads, or nonlinear behavior need fuller analysis.