Free Fabora tool
Use this free UK steel beam calculator (sometimes called an RSJ calculator) to compare mild steel RSJ, UB, UC, SHS and RHS sections for practical planning checks. Choose a simply supported, cantilever, or fixed beam case, enter the span and load, and view beam self weight, bending moment, estimated deflection, and an indicative bending stress estimate.
Free Fabora tool
Steel beam load and deflection estimate
For fabricators, site welders, steel erectors, mezzanine fitters and the office — anyone who wants a quick universal beam load calculator, fixed beam calculator or steel beam deflection calculator figure without the faff.
Use note
Planning only, not beam approval
Indicative planning calculator only. This tool gives a quick estimate for beam self weight, bending moment and deflection from the inputs shown. It does not certify a beam, confirm compliance, or replace structural design. Final beam selection, checks and approval must be completed by a qualified structural engineer or competent designer.
Use the tool
Pick the support type, the load type, the section family and the size, then type in your span and load in whatever units suit you. You get back self weight, total beam weight, the applied load in kN, the maximum bending moment, an estimated deflection and a bending stress comparison — with every assumption it's made laid out next to the result.
Inputs
Pick the beam case, choose a section, then enter the span and load to run the estimate.
Results
Choose the beam case and section, then add the span and load to see the estimate.
What it helps with
Use it for the early back-and-forth on a job — what section, how heavy, how much it'll deflect, roughly what stress — while you're still working out which way the design is going.
Good fit for
Quick checks on span, section size and rough loading.
Workshop, office or out on site — wherever the steel talk happens.
You'll see self weight, bending moment, deflection and a rough bending stress figure in seconds. It's the kind of back-of-the-envelope check you'd do before ringing the engineer or sizing a lintel over a doorway.
SHS, RHS, UB and UC. No PFC, no angle, no exotic grades in this version. Just the box and I-sections that turn up on most steelwork jobs.
Simply supported, cantilever or fixed. Drop a point load on it, or spread a total load across the whole span. That's the lot for now.
This is a planning number, nothing more. It doesn't certify the beam, it isn't a design, and it's no replacement for a structural engineer putting their name to the calcs.
Where it fits
We've kept it tight on purpose. It gives you a sensible beam estimate for the usual sections and simple load cases. It doesn't pretend to be a design package, and it won't sign anything off.
Sizing up a beam before you cut steel, price a job, or get the designer on the phone. Punch in the span and load and you've got a number to work from.
Standing under a span working out if a section looks about right, or whether a load case is one to flag before anyone lifts it into place.
When you just want a quick beam or RSJ load figure for a quote and don't fancy firing up a full structural package to get it.
Related Fabora tool
If all you're really after is the weight of the section, not the moment or the deflection, the Steel Weight Calculator does SHS, RHS, UB, UC, PFC, plate and the rest.
Tool FAQ
The questions people tend to ask before they trust a steel beam calculator, universal beam load calculator or RHS or SHS load calculator on a real job — including how the indicative bending stress comparison is worked out.
Keep moving
After more steelwork tools, or help with the paperwork side of a job? There's the full Fabora RAMS product, plus the rest of the Tools section.
Mild steel SHS, RHS, UB and UC, on simply supported, cantilever or fixed beams. Load it with a point load or a total load spread over the span. Out the other end you get self weight, total beam weight, the maximum bending moment, an estimated deflection and a rough bending stress figure to compare against.
RSJ is short for Rolled Steel Joist, the old-school name a lot of people still use for a structural steel beam. These days most beams are universal beams (UB) or universal columns (UC), both of which this tool handles, so when someone asks for an RSJ calculator they're really after a steel beam calculator. Same thing.
For the rough early-planning sums people usually mean by that, yes, it'll help. But it's an indicative figure only. The actual beam choice, the proper checks and the sign-off all sit with a structural engineer or a competent designer.
It'll give you bending moment, deflection and a stress comparison so you can hold two or three sections up against each other early on. What it won't do is size the beam for you or stand in for proper calcs signed off by an engineer.
The UDL you type in is taken as one total load spread evenly down the whole span, not as kN per metre. So if you've got 20 kN across the beam, enter 20, not the per-metre figure. The input box and the result note both spell that out so nobody gets caught out.
It does. You get self weight in kg per metre and the total weight over your span, and the beam's own weight gets thrown into the moment and deflection sums as a load running the full length. So the steel isn't pretending to be weightless.
Yes. It takes the maximum bending moment, divides through by the section modulus and compares that against the steel grade you picked. Treat it as a rough yardstick, not proof the beam is safe.
Box sections pull their dimensions from Fabora's section library, then the second moment of area and section modulus are worked out from the outside size and the wall thickness. It treats the corners as square, so it ignores the corner radius, which means the figures sit slightly on the cautious side.
UB and UC pull from a stored table of properties for common UK sizes. Rolled sections aren't simple rectangles, so trying to derive their properties from box-section maths would throw the numbers out. A lookup table keeps them honest.
Indicative planning calculator only. This tool gives a quick estimate for beam self weight, bending moment and deflection from the inputs shown. It does not certify a beam, confirm compliance, or replace structural design. Final beam selection, checks and approval must be completed by a qualified structural engineer or competent designer.