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Beam deflection calculator

Mid-span deflection for a simply supported beam under a uniform load. Uses the standard 5wL⁴ / (384·E·I) formula. Includes the L/360 (interior finish) and L/240 (general live load) IBC serviceability checks. Sanity-check only — a stamped design is your structural engineer’s job.

I = 204 in⁴, E = 29,000,000 psi (auto-set from preset; switch to Custom to override)
Mid-span deflection
0.631 in≈ L/456
L/360 (interior finish): PASS — limit 0.800 inL/240 (general): PASS — limit 1.200 in
Formula: δ = 5·w·L⁴ / (384·E·I). Uniform load only. Not valid for point loads, cantilevers, or fixed-fixed connections.
How it works

For a simply supported beam with a uniformly distributed load w (force per unit length) over span L, the maximum mid-span deflection is δ = 5wL⁴ / (384·E·I). We hold I and E in consistent units (in⁴ and psi), convert your input span from ft to in, and your input load from plf to pli.

Presets cover the most common shapes pulled in commercial framing: W12×26 + W14×30 steel, 2x10 + 2x12 DF-L #2 wood, and a generic Glulam 6.75x12. For anything unusual, override I and E directly.

Built by Forward

Beam math over text — same answer, no spreadsheet.

Forward is a phone number your field crew + PMs text. The bot runs beam deflection, steel section weight, bolt allowable shear, plus the NEC / IBC / IMC / IPC calcs you normally pull a book for. It also reads RFIs, drawings, submittals, change orders, and daily logs from Procore + Autodesk + OneDrive.