Beam Deflection Calculator
Reviewed by Hamza Gujjar, Algorithm Architect & Software Developer
Last updated: July 27, 2026Beam Deflection Calculator
How much will a beam bend under load? This calculator computes maximum deflection for the most common structural scenario - a simply supported beam with a point load at its center.
Deflection = (Load × Length³) / (48 × E × I)
Example
A 1,000 N load at the center of a 2 m steel beam (E = 200 GPa, I = 8├ù10Ôü╗ÔüÀ mÔü┤):
Maximum Deflection ≈ 1.04 mm
Why Span Length Matters So Much
Deflection grows with the cube of beam length - doubling an unsupported span increases deflection eight-fold under the same load and cross-section, which is exactly why longer spans require disproportionately larger, stiffer beam cross-sections (higher moment of inertia) to keep deflection within acceptable design limits.
The Two Material/Shape Factors
Elastic modulus (E) reflects the material's inherent stiffness (steel is much stiffer than aluminum, for instance), while moment of inertia (I) reflects how the cross-section's material is distributed relative to the bending axis - both factors appear in the denominator, meaning increasing either one directly reduces deflection.