Engineering

Beam Deflection (Center)

Simply supported beam, point load: δ = PL³/(48EI)

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Load P (N)

Span L (m)

Modulus E (GPa)

Moment I (cm⁴)

Allowable deflection is often L/250…L/400 — check applicable codes.

How it works

Calculate mid-span deflection of a simply supported beam under a center point load.

Who it's for: Structural engineers and students in mechanics of materials.

Formula: δ = PL³/(48EI) for a pin-supported beam with load P at center.

Also shows δ/L ratio and maximum moment M = PL/4.

E in GPa; I in cm⁴ (converted internally).

Enter Load P (N), Span L (m), Modulus E (GPa), and Moment I (cm⁴).
Read Deflection δ in mm and compare δ/L to allowable limits (often L/250–L/400).