Beam Load Calculator

Enter the span and load of a simply supported beam (resting on two end supports) to find the maximum bending moment and reaction force at each support.

Beam Load Calculator

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Beam span (ft)

Load type

Load (lb/ft)

Max bending moment

6,250 lb-ft

Reaction at each support

2,500 lb

Total load

5,000 lb

Assumes a simply supported beam - resting freely on two end supports, not fixed or continuous over multiple spans.

The formulas

Uniform distributed load (w, in lb/ft): Max moment = w x L^2 / 8 Each reaction = w x L / 2 Centered point load (P): Max moment = P x L / 4 Each reaction = P / 2

Example

A 10 ft simply supported beam with a uniform 500 lb/ft load: max moment = 500 x 100 / 8 = 6,250 lb-ft, and each support carries 2,500 lb.

Step-by-step guide

Enter the beam's span - the distance between its two supports.
Choose the load type - a uniform load spread evenly along the beam (like a floor load), or a single point load concentrated at the center.
Enter the load value and read the maximum bending moment and support reactions.

What bending moment tells you

Maximum bending moment is a key input for checking whether a specific beam (of a given material and cross-section) is strong enough for a load - engineers compare it against the beam's section modulus and material strength to verify it won't fail or deflect excessively. This calculator gives you the moment and reactions; translating that into "is this exact beam strong enough" requires the beam's specific material properties and cross-sectional shape, which varies by product.

Note: This calculator handles a simplified, idealized case (simply supported, single load type) for educational and preliminary planning purposes. Real structural design - especially anything load-bearing in a building - should be verified by a licensed structural engineer, accounting for load combinations, safety factors, local building codes, and the specific beam material and cross-section.

Common mistakes

Applying the uniform load formula to a load that's actually concentrated at one point, or vice versa - the two produce meaningfully different moment and reaction values for the same total load.

Forgetting the beam's own weight as an additional uniform load on top of whatever it's supporting, especially for longer spans or heavier beam materials.

Frequently asked questions

What does "simply supported" mean?

It means the beam rests freely on two end supports (like a beam sitting on two posts), free to rotate slightly at each end, as opposed to being rigidly fixed or continuous across multiple spans - those other configurations use different formulas.

Why does a point load create twice the moment of an equal total uniform load?

Concentrating the same total weight at a single center point creates more bending stress than spreading it evenly along the beam, which is why the point-load formula (PL/4) gives a larger moment than the uniform-load formula (wL²/8) for the same total force.

Do I need to know the beam's material to use this calculator?

Not for the moment and reaction figures shown here - those depend only on span and load. Material and cross-section matter for the next step: checking whether a specific beam can actually handle that moment without failing or deflecting too much.

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