About this tool
The Beam Deflection Calculator is a free, in-browser structural tool that returns the maximum deflection and slope of a single-span beam using the closed-form Euler-Bernoulli solutions. Pick the support condition (simply-supported, cantilever, or fixed-fixed), the load type (a central point load P or a uniformly distributed load w), and enter the span L, the modulus of elasticity E, and the area moment of inertia I. Everything is computed locally in your browser, so nothing you type is uploaded.
Each case uses its standard formula. Simply-supported with a central point load gives maximum deflection δ = PL³/(48EI) and end slope θ = PL²/(16EI); with a UDL it is δ = 5wL⁴/(384EI) and θ = wL³/(24EI). A cantilever with an end point load gives δ = PL³/(3EI) and θ = PL²/(2EI); with a UDL, δ = wL⁴/(8EI) and θ = wL³/(6EI). Fixed-fixed beams are stiffer: δ = PL³/(192EI) for a central point load and δ = wL⁴/(384EI) for a UDL. The flexural rigidity EI drives every result, so the tool also reports it. Choose SI (metres, GPa, mm⁴, newtons) or imperial (inches, psi, in⁴, lbf) and the units convert consistently.
As a worked example, a simply-supported steel beam (E = 200 GPa, I = 10,000,000 mm⁴) spanning 3 m under a 10,000 N central load has EI = 2,000,000 N·m² and a maximum deflection of PL³/(48EI) = 10,000 × 27 / (48 × 2,000,000) ≈ 0.00281 m, or about 2.81 mm, with an end slope near 0.16°. These are elastic, small-deflection results for a prismatic beam of constant EI and should be checked against a stiffness or serviceability limit such as L/360.