Beam Reaction Calculator
A free, browser-based calculator. Runs entirely in your browser — no sign up, nothing stored.
Enter Values
How to use this calculator
- Enter the span length L — the distance between the two supports.
- Add a point load and where it sits (measured from the left support), a uniform load across the whole span, or both.
- Read the left and right support reactions and the total load instantly.
How it works
The Beam Reaction Calculator finds the vertical reactions at the two supports of a simply supported beam (a pin at one end, a roller at the other) carrying downward loads.
It takes moments about each support. A point load P at distance a from the left gives a left reaction of P(L − a)/L and a right reaction of P·a/L. A uniform load w over the span L adds w·L/2 to each support. Point and uniform loads are added together (superposition).
Worked example
6 m span, 10 kN at 3 m, plus 5 kN/m. Point load: 10×(6−3)/6 = 5 kN each side. Uniform load: 5×6/2 = 15 kN each side. Reactions: R₁ = R₂ = 20 kN; total load = 40 kN.
Tips
- Leave the point-load position blank to place it at mid-span (reactions split evenly).
- The two reactions should add up to the total load — a quick sanity check.
Frequently asked questions
What does ‘simply supported’ mean?
The beam rests on two supports — a pin (resists vertical and horizontal movement) and a roller (resists vertical only). The ends are free to rotate, so no moment is carried at the supports.
Can I add more than one point load?
This tool takes one point load plus one uniform load. For several point loads, work each one out separately and add the reactions — reactions superpose linearly.
Can I use these results for final design?
No. These calculators are for first-pass sizing, checking and learning. They assume ideal supports, static loads and elastic behaviour, and they don't apply load factors, member capacity, buckling or connection checks. Always verify against the relevant design code (e.g. AS 4100, AS 1170, Eurocode) and have a qualified engineer sign off structural work.
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Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.