DIY Projects
Illustrative Scenario: Coordinating Loft Conversion Steelwork
A fictional loft project showing how restricted access, a revised roof layout and differing quotation scopes affect coordination.
Free planning tools & plain-English guides
Your Complete Guide to RSJ Steel Beams
Free calculators, load tables and installation guides for Rolled Steel Joists. Plan your project, then confirm everything with a chartered structural engineer and Building Control.
50+ Practical Guides
8 Free Calculators
UK Focus + EU
Span 4.5m
Load 45 kN
Type Planning
Quick Access Tools
Everything you need for RSJ beam selection and installation
Free RSJ Calculators
Size, load, weight, deflection, span table, padstone, bearing length and cost — free to use
Calculate nowLoad Tables
Sourced section properties and explanations of load and deflection calculations
View tablesDIY Guides
Installation and knock-through planning guides with preparation checklists
Read guidesComparisons
RSJ vs alternatives, materials, finishes, and cost analysis for informed decisions
Compare optionsPopular free RSJ calculators
Start with the tool that matches your question — all free, no signup
Free RSJ calculator FAQ
Quick answers if you searched for an RSJ calculator free online
Is the RSJ calculator on RSJ.info free?
Yes. Size, load, weight, deflection, span lookup, padstone, bearing length and cost tools are free to use with no account. They are planning aids only — not a substitute for a chartered structural engineer or Building Control approval.
Which free calculator should I use first?
To explore the arithmetic, use the beam size calculator or span table lookup. Then check deflection and weight before asking for quotes.
Will Building Control accept calculator results?
No. Online results help you brief an engineer and budget the job. Use the project-specific design and documentation required by your building control body.
What size RSJ do I need for a 4 m span?
A 4 m opening does not determine a beam size. Loads, restraints, supports and serviceability requirements must be established by the engineer. Read the 4 m span guide and run the size calculator with your numbers.
Start Here
What Is an RSJ Beam? A Complete Beginner's Guide
New to structural steel? Our plain-English guide explains what RSJ stands for, how rolled steel joists work, section designations, quotation preparation, and how to brief a structural engineer for your project.
- What RSJ, UB and I-beam really mean
- Section sizes and illustrative budgets
- Engineer and Building Control requirements
Latest Articles
Guides with sources and worked examples
DIY Projects
Illustrative Scenario: Planning a Kitchen Knock-Through
A fictional kitchen alteration showing how load paths, support details and temporary-works responsibilities affect the design brief.
DIY Projects
Padstone Bearing Pressure: Comparing Assumed Contact Areas
Compare average pressure for two assumed bearing areas under the same force, and see which support checks the arithmetic leaves unresolved.
DIY Projects
What Size RSJ for a 6m Span? Information Your Engineer Needs
Why a 6m opening does not determine beam size, with an illustrative deflection calculation and a survey checklist.
Costs & Suppliers
RSJ Installation Labour: Comparing Contractor Quotes
Compare contractor quotes for temporary support, lifting, installation and making good, and identify exclusions before work starts.
Costs & Suppliers
RSJ Sizes and Prices: From Section Schedule to Quote
A size chart gives geometry and mass; a supplier quote gives a selling price for a defined order.
Need Professional Help?
All structural work should be designed by a qualified structural engineer and approved by Building Control. Our guides provide information only and don't replace professional advice.