Beam Load Calculator
A beam design checker, not just a math machine. Pick the support and load, set the material and section, and get the reactions, shear, moment, deflection, bending stress, safety factor, and a clear pass / fail against your stress and deflection limits.
Beam & loading
Shear, moment & deflection
From “what is the moment” to “will it hold”
A beam calculation is only useful if it answers the real question: is this member strong enough and stiff enough? This checker computes the support reactions, maximum shear, maximum bending moment and maximum deflection for your beam, then converts the moment into a bending stress, compares it to the material limit, and checks deflection against a serviceability ratio such as L/360. You get a single pass or fail plus every number behind it.
Beam formula chart
The classic closed-form results this tool reproduces (and extends to arbitrary loads using a finite-element solution):
Load diagram examples
A point load is a single concentrated force (a post or column landing on the beam). A uniform load (UDL) spreads evenly along the span, like floor or roof loading. Multiple point loads model several posts or joists, and a partial UDL covers only part of the span, such as a stored pallet load. The diagram above the results redraws to match what you entered, with the shear, moment and deflection curves below it.
Bending stress
Bending stress is the moment divided by the section modulus, and a design passes when that stress stays at or below the allowable bending stress of the material:
Deflection limits explained
Even a beam that is plenty strong can feel bouncy or crack finishes if it sags too far. Deflection limits cap the sag as a fraction of span:
| Limit | Typical use |
|---|---|
| L / 240 | Roof members, rough framing, total load |
| L / 360 | Floors and members supporting plaster or drywall ceilings |
| L / 480 | Stiffer floors, tile, or where bounce must be minimized |
| Custom | Project-specific or manufacturer requirement |
Strength vs. deflection — why both matter
Strength (stress) and stiffness (deflection) are separate checks. A long, shallow beam often passes the stress check but fails deflection, while a short, heavily loaded beam may do the opposite. Stress depends on the section modulus S; deflection depends on the moment of inertia I and the modulus of elasticity E. That is why this tool reports both and tells you which one governs.
Common beam materials
| Material | Modulus E | Allowable bending |
|---|---|---|
| A36 structural steel | 29,000,000 psi (200 GPa) | about 24,000 psi (165 MPa) |
| Aluminum 6061-T6 | 10,000,000 psi (69 GPa) | about 19,000 psi (131 MPa) |
| Douglas fir, No. 2 | 1,600,000 psi (11 GPa) | about 900 psi (6.2 MPa) |
| LVL | 2,000,000 psi (13.8 GPa) | about 2,600 psi (17.9 MPa) |
| Concrete (plain) | 3,600,000 psi (25 GPa) | about 500 psi (3.5 MPa, modulus of rupture) |
Values are typical working stresses for preliminary sizing. Always confirm against the governing code and the exact grade.
FAQ
What is section modulus vs moment of inertia? Moment of inertia (I) drives deflection and stiffness; section modulus (S = I / c) drives bending stress. The section helper computes both from your shape and dimensions.
Does it handle indeterminate beams? Yes. The fixed-fixed case is statically indeterminate and is solved with a finite-element method, so its reactions, moment and deflection are computed correctly rather than approximated.
Is the beam self-weight included? No — add the member self-weight to your distributed load if it is significant.
Related engineering calculators
Need to know how much the beam will bend? Pair this with the Beam Deflection Calculator for the stiffness and serviceability check.
All Engineering CalculatorsFull Calculator LibraryCross-links to the Moment of Inertia, Beam Deflection, Stress, Bolt Load and Mechanical Design calculators will activate as those tools go live in this category.
For preliminary estimating and learning only. Structural members must be designed and verified by a qualified engineer against the applicable building code. Results assume a straight, prismatic, elastic beam in a single plane and do not check shear stress, lateral-torsional buckling, web crippling, bearing, or connections.