How the beam calculator works: draw a span, drop in supports, apply loads — and read the reactions, shear force and bending moment straight off the diagrams. Worked example above: a simply supported beam, L = 6.00 m with a 20 kN point load at midspan, so R₁ = R₂ = F/2 = 10 kN and Mmax = F·L/4 = 30 kN·m.
Buildref is a free reference and toolkit for civil, structural and BIM engineers. Size a beam, check a roof pitch, convert a 3D model or look up a drawing symbol — every tool runs entirely in your browser, so nothing is uploaded and nothing is installed.
No account · No file uploads · No install · Free to use
Engineering tools
Everything below is client-side JavaScript. Your geometry, loads and 3D files are processed on your own machine and never sent to a server.
Beam & Frame Calculator
Reactions, shear force and bending moment diagrams for simply supported beams, cantilevers and 2D frames. Point loads, UDLs and multiple spans.
Open calculator → CalculatorRoof Pitch Calculator
Convert between degrees, slope percentage and X:12 pitch, and get rafter length, rise and run for any roof.
Calculate pitch → 3DFree Online 3D Viewer
Open STL, OBJ, GLB and glTF models straight in the browser. Orbit, zoom and inspect geometry without AutoCAD, Revit or a plugin.
Open viewer → ConverterSTL ↔ OBJ Converter
Convert mesh files in both directions. Binary and ASCII STL supported, and the file never leaves your computer.
Convert now → ConverterOBJ ↔ GLB Converter
Pack OBJ geometry into a single compact GLB file for web viewers, AR and sharing models with clients.
Convert now → UnitsEngineering Unit Converter
Length, area, volume, force, pressure and moment — metric and imperial, at full working precision.
Convert units →All 3D converters All calculators Greek letters & symbols
Popular guides and references
Worked examples, formulas and reference tables written for people who actually have to hand in the drawing.
Engineering Drawing Symbols — Complete List
Welding, surface finish, GD&T, section and dimension symbols in one searchable reference with meanings.
Read the reference → StructuralBeam Load Calculations — Step by Step
How to go from tributary area to a design load, with the formulas for reactions, shear and bending moment worked through.
Read the guide → StructuralHow to Tell If a Wall Is Load-Bearing
The load-path checks, joist direction, wall thickness and the signs that mean you need a header beam before you knock anything out.
Read the guide → StructuralShear Force & Bending Moment Diagrams
How to draw SFD and BMD by hand for the standard load cases — and how to sanity-check what a solver gives you.
Read the guide → Road designRoad Gradient Calculation
Percentage, ratio and degrees — the formula, worked examples and the maximum gradients allowed by common design standards.
Read the guide → 3D formatsSTL vs OBJ — Which Format to Use
Geometry, colour, materials and file size compared, plus which format to hand over for printing, rendering or coordination.
Compare formats →Browse by topic
Four working areas, one reference site.
Why engineers use Buildref
Your files stay on your machine
Every converter and the 3D viewer run on WebGL and JavaScript in your own browser. Nothing is uploaded, so client models and confidential geometry never touch a server.
The formula is always shown
Calculators print the equation they used, not just a number — so you can check the result by hand, cite it in a report or hand it to a reviewer.
No account, no paywall
Nothing to register for and nothing to install. Open the page, get the answer, close the tab. The site is funded by advertising, not by locking tools behind a login.
Frequently asked questions
Is the beam calculator free to use?
Yes. The beam and frame calculator, the 3D viewer, all converters and all calculators are free and need no account. There is no usage limit and no watermark on results.
Are my 3D files uploaded to a server?
No. The STL, OBJ, GLB and glTF converters and the 3D viewer parse the file locally in your browser using JavaScript. The file is never transmitted, which is why the tools also work with confidential client models.
Which units does the beam calculator use?
Metres and kilonewtons by default: spans in m, point loads in kN, distributed loads in kN/m, moments in kN·m. The unit converter handles imperial input if you need to work in feet, pounds or kip.
Can I use these results for a real design?
Use them for sizing studies, checks and learning. Buildref shows the formulas so the maths is auditable, but a final structural design still has to be signed off by a qualified engineer against the code that applies in your jurisdiction.
Does the site work on a phone or tablet?
Yes. The calculators and references are responsive. The 3D viewer and converters need WebGL, which works on current iOS and Android browsers, though very large meshes are easier to handle on a desktop.
The information and tools on Buildref are provided for educational and reference purposes. Always verify critical calculations against the applicable design code and have them checked by a qualified engineer.