Beam Deflection Calculator

Work out the maximum deflection of a straight beam under a point load or a uniformly distributed load, for a cantilever or a simply-supported (pin-roller) span. Pick the support, the load, the material (for Young's modulus) and the cross-section, and the tool gives the area moment of inertia, the maximum deflection, and the deflection-to-span ratio compared with the common L/360 live-load and L/240 total-load limits. The standard Euler-Bernoulli formulas apply: cantilever end point load PL³/3EI, cantilever UDL WL³/8EI, simply-supported centre point load PL³/48EI, and simply-supported UDL 5WL³/384EI. Useful for sizing floor joists, shelves, brackets and machine frames. Pure arithmetic — small-deflection theory that assumes linear-elastic material, a prismatic section, and loads well below yield; it ignores shear deflection (short beams) and self-weight unless you add it. Everything runs locally in your browser.