BEAMS & DEFLECTION

Simply Supported Beam Calculator

Find reactions, bending stress and maximum deflection for a rectangular beam under a central point load.

SI & US customary units Live results Inputs stay in your browser

Input parameters

Illustrative input, not a certified material property.

Values are calculated locally in your browser.

Results

Live calculation
Maximum deflection
0.2 mm

Theoretical result · verify applicability below

Maximum bending stress6 MPa
Maximum bending moment500 N·m
Second moment of area4,166,670 mm⁴
Reaction at each support500 N

Engineering model

PLdeflection (exaggerated)

Schematic illustration · not to scale

Formula & method

RA = RB = P/2 · Mmax = PL/4 · I = bh³/12 · σmax = Mmax(h/2)/I · δmax = PL³/(48EI)

A centered point load splits equally between two simple supports. The largest bending moment and downward deflection occur at midspan. Section height is measured in the bending direction; doubling it increases stiffness by a factor of eight.

Worked example

P = 1,000 N, L = 2 m, E = 200 GPa, b = 50 mm and h = 100 mm give I = 4.16667 × 10⁶ mm⁴, each reaction = 500 N, Mmax = 500 N·m, stress = 6 MPa and deflection = 0.2 mm.

The initial inputs reproduce this example. Material values are illustrative inputs, not a material database or certified design values.

Assumptions & limitations

Prismatic rectangular beam, ideal pin and roller supports, linear elasticity and small deflections under a static central load. Self-weight, shear deformation, lateral torsional buckling and stress concentrations are excluded.

No factor of safety or design-code allowance is applied unless explicitly stated. Read the engineering disclaimer before applying these results.

Checking your calculation

Confirm the load direction and units first. Check the schematic against your actual supports and geometry, then compare the worked example with your own independent calculation. A valid numerical result does not establish that the model is appropriate for a real component.

For background, consult the Air Force Stress Analysis Manual’s column analysis and MIT’s Mechanics of Materials learning modules. Use applicable design standards and certified material data for real designs.