Steel fabrication estimating is pricing supplied-and-fabricated steelwork from the drawings: take off every member, convert it to weight, then apply rates for supply, shop labour, coatings, drafting and margin. The structure is simple - estimate = take-off × rates - and every serious structural steel cost estimation follows it, whether it's done on paper, in a spreadsheet or with a free estimating tool. What separates a good estimate from a bad one is almost always the fabrication hours.
Steel supply prices are published and coating rates are quotable, but fabrication hours live in the estimator's judgement - and they vary by a factor of four between job types. Indicative ranges for Australian shops:
| Type of work | Hours per tonne | Why |
|---|---|---|
| Heavy, simple beamwork (columns and beams, standard end plates) | 8 – 12 | Big tonnes, few operations per member |
| Portal frame sheds and typical commercial framing | 15 – 20 | Haunches, bracing, purlin cleats, moderate repetition |
| Trusses and lighter framed work | 20 – 30 | Many light members, lots of cutting and welding per kilo |
| Stairs, handrails, balustrades, architectural | 25 – 40+ | Fiddly, light, finish-critical - hours with hardly any tonnes |
Indicative only - your shop's history on similar jobs beats any table. At a shop rate of $80–$110/hr, fabrication alone adds roughly $1,000–$2,500+ per tonne to the steel.
This is why quoting from a single blended "dollars per tonne" figure without looking at the drawings is dangerous: two jobs of identical tonnage can differ by thousands per tonne purely on hours. The tonnage tells you what you'll buy; the drawings tell you what you'll spend.
The hourly rate the hours get multiplied by has to carry more than wages: supervision, workshop overheads and equipment, welding consumables and gas, grinding discs, power, insurance and compliance. Most Australian shops land somewhere in the $80–$110/hr range as a fully-absorbed rate. Charging bare wages as your shop rate is the quiet way estimates lose money.
Supply, coatings, drafting and bolts are more mechanical - each is a published or quotable rate against a quantity the take-off already produced. Current indicative Australian ranges for all of them, with a fully worked example, are on the structural steel cost per tonne page.
Experienced estimators still use blended per-tonne figures - just not for quoting. They're the cross-check at the end: if a galvanised portal-frame shed prices out at $3,000/t supplied-and-fabricated, something's been missed; if plain beamwork comes out at $9,000/t, something's been double-counted. Build the estimate bottom-up, then stand back and ask whether the per-tonne result is believable for the type of work.
All of the above is arithmetic against lookup tables - exactly what software is for. The free Steel Quote calculator runs the whole method in your browser: pick sections from the built-in Australian lists (weights and painting areas fill in automatically), set your own supply, fabrication, coating and drafting rates, and it produces the totals live as the take-off grows. You can measure straight off a PDF drawing, and export the finished estimate as an Excel spreadsheet or a print-ready PDF. It's free, with no sign-up, and nothing you enter leaves your machine.
Take off the steel from the drawings, convert to weight, then price supply per tonne, fabrication as hours per tonne × shop rate, coatings, drafting, bolts and margin. Never price from floor area or a guessed lump sum.
Labour alone is commonly $1,000–$2,500+ per tonne depending on complexity. All-in supplied-and-fabricated steel typically lands around $4,000–$7,000+ per tonne in Australia - see cost per tonne for the breakdown.
With a complete take-off and honest hours, well within normal margin. The big misses come from skipped members, painted area priced from weight, and hours per tonne borrowed from a different type of job.
Steel Quote is a free structural steel take-off and cost estimation calculator built for the Australian fabrication industry. Enter your members, set your own rates, and export a working estimate as a PDF or Excel spreadsheet - no sign-up, and your data never leaves your browser.