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Beam Load Calculator
Calculate maximum bending moment, shear, and deflection for a simply supported beam under point or distributed loads, as a preliminary check.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
Math & Science
Beam Load Calculator
Frontend preview — no upload or external service.
Result
4.2 m span with 8 kN/m UDL: maximum moment 17.6 kNm at midspan, reactions 16.8 kN each end, deflection about 9 mm — span/467, within a typical span/360 limit.
How the Beam Load Calculator works
- Enter the clear span between supports, not the overall beam length.
- Add the load, distinguishing dead load from imposed load with the appropriate factors for your code.
- Check deflection as well as strength — beams usually satisfy bending long before they satisfy a deflection limit.
The method
For a simply supported beam with a uniformly distributed load, the maximum moment occurs at midspan and grows with the square of the span.
M = wL²/8 for a UDL; M = PL/4 for a central point load
At 8 kN/m over 4.2 m: 8 × 4.2² / 8 = 17.6 kNm. Doubling the span quadruples the moment, which is why span drives beam sizing more than load does.
FAQ
Why does deflection usually govern?
Because deflection grows with the fourth power of span while bending grows with the square. A beam strong enough to carry the load often still bounces or cracks finishes, which is what deflection limits exist to prevent.
What deflection limit should I use?
It depends on what the beam supports and which code applies — span/360 is common for members carrying brittle finishes, span/250 for others. Your local structural code sets the requirement.
Can I use this for a real building?
No. This is a preliminary check using textbook formulas for an idealised simply supported beam. Real structures involve load combinations, continuity, lateral restraint, and code compliance, and need a qualified structural engineer.
How we compare
| Feature | Online Tool Store | A graphing calculator | A stats package |
|---|---|---|---|
| Bending and deflection together | ✓ | One at a time | ✓ |
| Shows the formula | ✓ | ✗ | Sometimes |
| No software licence | ✓ | ✓ | ✗ |
| Structural sign-off | ✗ | ✗ | ✓ |
Beam Load Calculator is a preliminary check on an idealised beam — anything that gets built needs a structural engineer and a code check.