Is this suitable for designing a real beam?
No. It is an educational estimate using the textbook formula for one simple case. Real design needs code-based load factors, multiple load cases and a qualified structural engineer.
// engineering › Civil
Simple Beam Deflection Calculator (Point Load, Centre)
Estimate midspan deflection of a simply-supported beam under a central point load, using the standard PL³/48EI formula. Educational use only — not for design.
δ = P L³ / (48 E I) (simply supported, central point load)
Frequently asked questions
What case does it cover?
A simply-supported beam (resting on a support at each end) carrying a single point load right at the centre. The deflection is greatest at midspan, which is what it reports.
What is the formula?
Deflection equals P L cubed over 48 E I, where P is the load, L the span, E the material's stiffness (Young's modulus) and I the cross-section's moment of inertia.
Why does span matter so much?
Because deflection depends on the span cubed. Doubling the span makes the beam sag eight times as much, all else equal, which is why long spans need much stiffer sections.
What are E and I?
E (Young's modulus) measures how stiff the material is, around 200 GPa for steel. I (moment of inertia) measures how the cross-section's shape resists bending, bigger for deeper sections.