Formula
Simply supported, centre point load: deflection = P x L cubed / (48 x E x I). Simply supported, uniformly distributed load: 5 x w x L to the power 4 / (384 x E x I). Cantilever, end point load: P x L cubed / (3 x E x I). Cantilever, uniformly distributed load: w x L to the power 4 / (8 x E x I).
Standard / source
Standard beam-deflection cases of the form published in the AISC Steel Construction Manual, Table 3-23, cited by reference only in the MetalCalz tool-expansion research (2026-10-27). The table itself is not reproduced here.
Worked example
Simply supported beam, centre point load 10 kN, span 4 m, E = 200 GPa, I = 2000 cm4 (= 2 x 10 to the power -5 m4): E x I = 4,000,000 Nm2. Deflection = 10,000 x 64 / (48 x 4,000,000) = 0.003333 m = 3.33 mm. Span-to-deflection ratio = 4000 / 3.33 = L / 1200. These are the calculator defaults.
Safety note
Safety-critical screening only: qualified-person gate. This checks sag only; it does not check bending strength, shear, connections, vibration or stability, and it does not approve a beam. Deflection limits such as L/240, L/360 or L/480 are project and code dependent, not universal. A qualified structural engineer must verify the full design under the applicable code before any real structure is built.