Category · Structural
Structural Calculators — Beam Deflection (IBC L/360 Checks)
Free structural beam deflection calculator for simply supported, cantilever, fixed-fixed, and propped beams — with live diagrams, IBC limit checks, and steel, wood, aluminum, and concrete presets.
IBC Table 1604.3 guide
Structural calculators for beam deflection and code checks
The beam deflection calculator covers simply supported, cantilever, fixed-fixed, and propped beams under point, uniform, and moment loads — with combined loading by superposition, live deflection/moment/shear diagrams, and IBC Table 1604.3 limit checks in SI and Imperial units. Enter span, stiffness (E from steel, aluminum, wood, and concrete presets; I direct or from the section helper), and loads to get peak deflection, reactions, bending stress, and a green-or-red code verdict.
Support types and the stiffness between them
Simply supported beams — floor joists on two walls — share curvature across two supports and forgive modest spans. Cantilevers carry everything on one fixed end and deflect 16× more for identical P, L, E, and I, so balconies and overhangs live under the L/180 limit with short arms and deep sections. Fixed-fixed frames are 4–5× stiffer when connections truly develop moment; propped ends model the honest middle. For deep dives, open the simply supported beam guide and the cantilever beam guide.
IBC limits, steel sections, and strength checks
IBC Table 1604.3 draws the lines: L/360 floor live load, L/240 total, L/480 tile and brittle finishes, L/180 cantilevers — compare every ratio in the allowable deflection limits guide. Steel work enters AISC W-shape inertia directly (W12×26 = 204 in⁴ at E = 200 GPa); wood, aluminum, and concrete use presets or the rectangular/circular section helper. And deflection never proves strength: check bending stress σ = M·c/I and shear on the same inputs, with derivations in the beam deflection formula reference and numbers in the worked examples guide.
Guides
Go deeper
How to Calculate Beam Deflection
Bench, steel beam, balcony, fixed-vs-supported examples.
Beam Deflection Formulas
All 10 cases: SS, cantilever, fixed, propped.
Allowable Deflection Limits
L/360, L/240, L/480, L/180 chart with inch examples.
Simply Supported Beams
Joists and lintels on two walls — formulas + checks.
Cantilever Beams
Balconies and overhangs — 16× rule, L/180, wall moments.
FAQ
Structural calculator questions, answered
What is the difference between L/360, L/240, and L/480?
L/360 limits floor live-load sag, L/240 covers total dead-plus-live load, and L/480 protects tile and brittle finishes. Smaller denominator means a tighter limit.
How do I size a steel beam with this calculator?
Enter the AISC W-shape inertia (e.g. W12×26 = 204 in⁴) with steel E = 200 GPa, apply span and loads, then check L/360 deflection plus bending stress.
Does passing deflection mean the beam is strong enough?
No — deflection is serviceability. Check bending stress σ = M·c/I and shear separately; this calculator reports both so each check runs on the same inputs.
Simply supported vs cantilever — what is the difference?
Two supports share curvature; one fixed end takes it all. A cantilever deflects 16× more than a simply supported beam for identical load, span, E, and I — keep cantilevers short.
Fixed vs pinned supports — how much stiffer?
Fixed-fixed ends are 4× stiffer for point loads and 5× for uniform loads versus pinned, when connections truly develop moment. Real connections land between; propped ends model the middle.
How do I get E and I for my beam?
E comes from material presets: steel 200 GPa, aluminum 69 GPa, SPF wood 9.65 GPa, concrete near 25 GPa. Enter I directly (W12×26 = 204 in⁴) or compute it with the section helper (rectangle I = b·h³/12).
Can I combine point and uniform loads?
Yes — linear superposition adds each load's deflection for small elastic deflections. Tick combine loads in the calculator to superpose a point load with a full-span uniform load.
Why do beam calculators disagree?
Support assumption (modeling fixed as pinned under-reads up to 4×), mixed units (GPa vs psi, mm vs inches), and partial versus full uniform load extent. This page shows every formula and EI used.