Last updated: April 13, 2026

Beam Deflection Calculator

Based on 3 sources
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Table of contents

Understanding beam deflection formulas

The fetched OmniCalculator beam deflection page explains that deflection depends mainly on four things: beam length, applied load, modulus of elasticity, and area moment of inertia. The longer and more heavily loaded the beam is, the more it sags; the stiffer it is, the less it moves.

Simply supported midspan load: δmax = P × L³ / (48 × E × I)

Cantilever end point load: δmax = P × L³ / (3 × E × I)

Simply supported uniform load: δmax = 5 × w × L&sup4; / (384 × E × I)

Material stiffness and flexural rigidity

Omni emphasizes why E and I sit in the denominator of every equation: together they form the beam's flexural rigidity EI. A larger value means the member resists bending more effectively.

This is why the same span and load can behave very differently in steel, aluminum, timber, or concrete.

Supported load cases in this rebuild

For simply supported beams, this batch includes the load configurations listed on the fetched Omni page: midspan point load, point load at any position, uniform load, uniformly varying load, triangular load, and a moment load at one support. It also includes the classical cantilever cases referenced by the article's FAQ.

ft
lb
psi
Use the bending axis moment of inertia that matches the direction of deflection.
in^4

Keep units consistent: span in feet is converted internally to inches so it works with psi and in&sup4;.

0.0179
in
0.454
mm
L/8056
3,480,000,000
lb*in^2

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