Steel Takeoff for General Contractors: A GC's Guide
A steel takeoff for a general contractor is a count of every structural member on the S-sheets, by size and length, rolled up into tons. GCs do one for three reasons: to budget a job before design is done, to check that steel sub bids cover the same scope, or to price a small package they plan to self-perform. Each purpose needs a different level of detail.
Most GC estimators aren't steel estimators, and they don't need to be. You don't have to detail connections or nest stock lengths to know whether a bid at 48 tons is light when the drawings show 61. You need a defensible count, a tonnage, and a clear list of what each sub included. This guide covers how to get there.
Why would a GC do its own steel takeoff?
Steel is often one of the largest single subcontracts on a commercial building, and it sits on the critical path. If the low steel bid is low because it left out the misc metals or the roof screen frame, you find out after award, and that becomes your problem.
There are a few concrete reasons GCs run their own numbers:
- Bid day sanity check. Three steel bids come in at $1.18M, $1.31M and $1.62M. Without your own tonnage you can't tell whether the spread is pricing or scope.
- Owner budgets. At schematic or DD, the owner wants a number. A rough tonnage from the framing plans beats a square-foot guess.
- Value engineering conversations. When the owner asks for cuts, you need to know where the tons are.
- Self-perform. Some GCs erect small steel packages or misc metals with their own crews. You can't price what you haven't counted.
- Change order review. When a sub claims a revision added 9 tons, your own baseline lets you check it.
If you'd rather not count members by hand, upload the S-sheets to SteelFlo and get your own member count and tonnage to level steel bids. The first 3 takeoffs are free.
Budget, bid check, or self-perform: which takeoff do you need?
These are three different jobs. Doing a self-perform level of detail for an early budget wastes days. Doing a budget-level number for a self-perform package loses money.
| Purpose | When | Detail needed | Typical output | Time to spend |
|---|---|---|---|---|
| Conceptual budget | SD / early DD | Tons by system (floor framing, roof, columns, lateral) | Tons x installed $/ton | Hours |
| Bid check / leveling | Bid day | Member count and tons by size, scope checklist | Tonnage per bidder, scope matrix | Half a day |
| Self-perform package | Before you commit to the work | Full count, lengths, connections, misc items, erection plan | Priced BOM plus labor | Days |
For conceptual budgets, a rules-of-thumb approach works fine. Our guide to steel per square foot gives typical pounds per square foot by building type, and conceptual steel estimating rules of thumb covers how to turn that into a budget. Once you have real framing plans, switch to a count.
What goes into a GC-level steel count?
You need a steel takeoff that answers four questions:
- How many pieces of each size? (e.g., 42 W16X26, 18 W24X68, 36 HSS6X6X1/4 columns)
- How long are they? Grid spacing gives you most beam lengths.
- How much do they weigh? Weight per foot is in the designation for W shapes. A W16X26 is 26 lb/ft.
- What's not on the framing plans? Lintels, embeds, roof frames, stair framing and the rest of the misc package.
Tonnage math is simple. For a W16X26 at 30 ft:
26 lb/ft x 30 ft = 780 lb per piece
Forty-two of them is 32,760 lb, or 16.4 tons. Repeat by size, add it up, and add an allowance for connection material. Many estimators carry somewhere in the range of 5 to 10 percent of main member weight for plates, clips and bolts on simple-framed buildings, and more on moment frames. Use your own history if you have it.
You can check weights for any size in the steel weight calculator or on shape pages like W16X26 and W24X68.
How do you level structural steel bids by tons and scope?
Bid leveling for steel has two parts: normalize the price to tonnage, and normalize the scope so you compare like with like.
Step 1: Get each bidder's tonnage
Ask every steel bidder to state their tonnage on the bid form. Many will. If one won't, that's information too. Compare each to your own count.
Step 2: Build a scope matrix
List every scope item and mark what each bidder included, excluded or qualified. The AISC Code of Standard Practice (ANSI/AISC 303-22) defines what "structural steel" means by default when the contract doesn't say otherwise. Items it doesn't list as structural steel often turn into scope gaps, so put them on the matrix explicitly.
Step 3: Compare $/ton on a level basis
Here's a worked example with three bids on a two-story office building. Your count says 112 tons of structural steel plus a misc metals package.
| Item | Bidder A | Bidder B | Bidder C |
|---|---|---|---|
| Base bid | $1,180,000 | $1,310,000 | $1,620,000 |
| Stated tons | 98 | 114 | 116 |
| Metal deck | Excluded | Included | Included |
| Misc metals (stairs, rails, lintels) | Excluded | Excluded | Included |
| Embeds supplied | Excluded | Included | Included |
| Erection | Included | Included | Included |
| Shop drawings / connection design | Included | Included | Included |
| Raw $/ton (bid / stated tons) | $12,041 | $11,491 | $13,966 |
Bidder A looks cheapest, but their 98 tons is 14 tons short of your count, and they excluded deck, misc and embeds. Before you call anyone low, add plugs for every excluded item to put all three on the same scope, then ask Bidder A where the missing 14 tons went. They may have missed a level, read a schedule wrong, or left out the roof framing.
The raw $/ton row is only a starting point. Deck, misc metals and erection are priced on different bases, so compare $/ton on the structural steel line alone when you can get the bids broken out.
Our steel bid scope letter guide shows what a clean steel scope letter looks like from the sub's side. It's useful to know what you should be seeing.
What do GCs usually miss in a steel takeoff?
The framing plans are the easy part. Scope gaps hide in the details, the architectural sheets and the spec.
Misc metals
Stairs, railings, ladders, lintels, bollards, trench frames, elevator pit ladders and sill angles. These are usually in Division 05 50 00 and often show up on architectural drawings, not the S-sheets. See Division 5 metals estimating for the full list.
Connections
Connection material is real tonnage. If the engineer delegated connection design, the steel sub carries engineering cost too. Bids should say whether connection design is included.
Embeds and anchor rods
Who supplies them, who sets them, and who surveys them? Embed plates often sit on the concrete drawings. Anchor rods are typically supplied by the steel sub and set by the concrete sub, but confirm it in writing.
Metal deck and shear studs
Some steel subs include deck, some sub it out, some exclude it. Studs follow the deck, so check both.
Roof and mechanical framing
Roof screen frames, RTU dunnage and opening frames are often shown on mechanical drawings or called out as "by others." Make sure someone owns them.
Revisions
If the drawings were revised during bidding, confirm every bidder priced the same set. A sub that bid off Rev 0 while you're on Rev 2 isn't comparable.
Should a GC self-perform small steel packages?
Some GCs do, usually on small buildings or for misc metals and simple framing like canopies and lintels. Procore's overview of self-perform construction points out the main trade-off: you gain schedule control, but you carry a larger payroll that doesn't go away when work slows.
For steel specifically, here's what to check before you take it on:
- Erection safety rules. OSHA's steel erection standard (29 CFR 1926 Subpart R) covers fall protection, column anchorage, decking and hoisting. Your crew and site plan need to meet it.
- Crane access and picks. A W24X68 at 40 ft weighs 2,720 lb before rigging. Know your picks.
- Shop work. Self-perform usually means buying fabricated steel from a fab shop and erecting it yourself. You still need shop drawings, and someone has to check them.
- Certifications. Some owners and specs require AISC-certified fabricators or erectors. Read the spec.
- Warranty and coordination risk. If the steel sub would have carried the risk of field fixes, now you do.
The Colony Construction comparison of self-perform vs subcontracting steel erection is a useful read from a contractor's side of the decision.
A good rule: self-perform only what you've counted in full. A bid-check takeoff is not enough detail to carry the risk of the work.
What tools work for a GC estimator without a steel background?
You have four realistic options.
| Approach | Pros | Cons | Good for |
|---|---|---|---|
| Rules of thumb (lb/sf) | Fast, no drawings needed | Wide range, no scope detail | Early budgets |
| Manual count in a PDF tool | Cheap, you control it | Slow on big sets, easy to miss pieces | Small jobs |
| Hire a takeoff service | No staff time | Turnaround time, cost per job | Occasional big bids |
| AI steel takeoff | Fast count by size, traceable to drawings | You still review and add misc scope | Bid checks, budgets from real plans |
With an AI steel takeoff like SteelFlo's steel takeoff software, you upload the PDF drawing set and the software finds and boxes each steel member label on every page. You review the boxes, confirm or reject them, and export a BOM with counts and weights. The count is the number of boxed labels, so every piece traces back to a spot on the drawing. That matters when a sub asks where your number came from.
It works best on vector or CAD-exported PDFs, which is what most current S-sheets are. Expect to add misc metals that only appear in specs or on architectural sheets yourself.
How should a GC present its own steel number to subs?
Carefully. Your takeoff is a check, not a bid. A few habits that keep relationships good:
- Ask questions, don't accuse. "We're showing about 112 tons. Can you walk us through your 98?" gets a better answer than "You missed 14 tons."
- Share the scope matrix, not your price.
- Give every bidder the same chance to clarify before award.
- Don't shop one bidder's number to another.
Frequently Asked Questions
Do general contractors need to do their own steel takeoff?
Not always, but it helps on any job where steel is a big share of cost. Your own tonnage lets you level bids and spot scope gaps. On small jobs with one trusted sub, a quick tonnage check may be enough.
How do you compare steel bids that have different tonnages?
Normalize scope first, then compare $/ton. Add plugs for every excluded item so all bids cover the same scope. Then ask any bidder whose tonnage is far from yours to explain the difference before award.
What is a reasonable allowance for connections in a GC steel estimate?
Many estimators use roughly 5 to 10 percent of main member weight for simple shear connections, more for moment frames and braced frames. That's a rule of thumb. Your fabricator's history on similar jobs is a better source.
Can a GC self-perform structural steel erection?
Yes, if the crew, equipment and safety program meet OSHA Subpart R and any project certification requirements. Most GCs who self-perform steel stick to small, simple packages. Price it only from a full takeoff, not a budget number.
Is AI steel takeoff accurate enough for bid leveling?
It's a strong starting point when you review the results. You confirm each boxed member and add items that aren't labeled on the S-sheets. Test any tool on a past job where you know the final tonnage before relying on it.
What drawings do I need for a GC steel takeoff?
The structural set (S-sheets) for framing, the architectural set for misc metals, and the specs for scope. Mechanical drawings sometimes show dunnage and roof frames too.
Bottom line
A GC's steel number doesn't have to be fabricator-grade. It has to be good enough to catch a 14-ton gap on bid day and to tell the owner where the tons are. Get the member count and tonnage from the S-sheets, build a scope matrix, and level on the same basis. If counting is what's slowing you down, run the next bid set through SteelFlo free and use your review time on scope instead.