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Calixo

Beam Deflection Calculator

Find the maximum deflection of a simply supported beam under a center point load.

Inputs

Steel ≈ 200 GPa, aluminum ≈ 69 GPa, timber ≈ 11 GPa.

Saved Scenarios

— select 2+ to compare

Max Deflection (mm)

0.100

Spark says

How it's calculated

Formula

δ=PL348EI\delta = \dfrac{P L^3}{48 E I}
P
— Center point load
L
— Span length between supports
E
— Elastic (Young's) modulus of the material
I
— Second moment of area (moment of inertia) of the cross-section

What is the Beam Deflection Calculator?

This is the classic formula for maximum deflection of a simply-supported beam under a single center point load — one of the most common checks in structural and mechanical design to keep deflection within acceptable limits.

How to use it

  1. 1 Enter the applied point load at the center of the span.
  2. 2 Enter the span length between supports.
  3. 3 Enter the material's elastic modulus.
  4. 4 Enter the cross-section's moment of inertia (from beam tables or a section calculator).

Worked examples

1,000 N load, 2 m steel span

About 0.1 mm of deflection at midspan.

Try it

Limitations

  • •Only valid for a simply-supported beam with a single center point load — different support conditions or load types (uniformly distributed, offset loads) use different formulas.

Frequently asked questions

Where do I find the moment of inertia for my beam?

Standard structural shapes (I-beams, channels) list it in manufacturer tables; for simple rectangular sections, I = width × height³ / 12.