Rebar takeoffs and structural steel takeoffs are different trades doing different math. Rebar (Division 3, concrete reinforcing) is estimated in tons from bar schedules and bending lists, with lap and waste factors added. Structural steel (Division 5) is estimated as a piece count — each beam and column counted individually, then multiplied by catalog weight per foot.
Both end in "tons of steel," which is why owners, GCs, and new estimators mix them up constantly. Almost nothing else about them matches: not the drawings, not the units, not the software, and usually not the person doing the work. Here's the clean split.
Are rebar and structural steel the same division?
No. In the CSI MasterFormat that organizes nearly every US commercial spec book:
- Rebar lives in Division 3 — Concrete, primarily 03 21 00 (Concrete Reinforcing). It's part of the concrete package: the reinforcing supplier or the concrete sub carries it, and it gets bought with the foundations and slabs.
- Structural steel lives in Division 5 — Metals, primarily 05 12 00 (Structural Steel Framing), with steel deck, joists, and miscellaneous metals in neighboring sections.
The division line is a scope line. A steel fabricator bidding "all steel on the job" is bidding Division 5 — the 60 tons of rebar in the footings is someone else's problem, and saying so in your scope letter costs one sentence. The recurring gray areas: anchor rods (typically furnished by the steel fabricator, set by the concrete sub), embed plates in concrete (usually Division 5 furnishes, Division 3 installs), and dowels at slab-to-structure interfaces. Those three items cause more cross-division arguments than everything else combined.
How is a rebar takeoff done?
Rebar is a weight-and-length trade. The estimator works from the concrete drawings — footing schedules, slab plans, wall elevations, column schedules, and above all bar schedules (bending schedules) that list each bar mark with size, shape, and dimensions. The mechanics:
- Quantify each bar mark: count × length, from schedules and typical details.
- Convert to weight using bar unit weights — a #4 bar is 0.668 lbs/ft, a #8 is 2.67 lbs/ft, up to #18 at 13.6 lbs/ft.
- Add lap splices — bars come in stock lengths (commonly 20, 40, 60 feet), so continuous runs need laps, typically adding 5–15% to straight-bar tonnage depending on lap class and bar size.
- Add waste — cutting and fabrication loss, usually 2–5%.
- Add accessories — chairs, bolsters, tie wire, mechanical couplers — priced separately from tonnage.
- Price the total in dollars per ton, furnished-and-installed or supply-only, with detailing (the shop bending lists) by the rebar fabricator per industry standards from the Concrete Reinforcing Steel Institute (crsi.org).
The defining feature: rebar quantity is computed, not counted. Nobody counts 14,000 individual bars on a plan — the schedules and typical details generate the tonnage arithmetically, and factors cover the rest. The parallels to Division 5's own add-ons (drops, mill length rounding, connection allowances) are real, but the percentages and the logic behind them differ.
How is a structural steel takeoff done?
Structural steel is a piece trade. Every member on the job is an individual, identifiable object: this W16X31 from gridline A to B, that HSS6X6X3/8 column at B-2. The estimator counts pieces from framing plans and member schedules, takes a length for each, and multiplies by the catalog weight embedded in the designation — a W16X31 weighs 31 lbs/ft by name. Then connections, fabrication labor per piece, coatings, and erection get priced on top. The full walk-through is in what is a steel takeoff?
The defining feature is the opposite of rebar: the count is the count. Miss two beams and you're two beams short — no factor covers it. That's why structural takeoff quality lives and dies on finding every label on every sheet, and why the errors are discrete and traceable rather than smeared across a percentage.
Rebar vs structural steel takeoff — side by side
| Rebar takeoff | Structural steel takeoff | |
|---|---|---|
| CSI division | 03 21 00 (Concrete) | 05 12 00 (Metals) |
| Base unit | Tons, computed from schedules | Pieces, counted, × lbs/ft |
| Source drawings | Concrete/foundation plans, bar schedules, typical details | Framing plans, member schedules, sections |
| Key documents | Bending schedules, lap details | Beam/column schedules, connection details |
| Adjustment factors | Laps +5–15%, waste +2–5% | Connections +8–12% weight allowance; minimal cut waste |
| Material spec | ASTM A615 / A706 Gr 60 bar | ASTM A992 W-shapes, A500 HSS |
| Priced by | $/ton, F&I or supply-only | $/ton material + per-piece fab + erection |
| Typical 2026 price sense | Roughly $1,400–$2,400/ton F&I in most US markets | Roughly $3,500–$7,000/ton fabricated & erected (detail) |
| Who estimates | Rebar fabricator / concrete sub | Steel fabricator / Division 5 estimator |
| Detailing standard | CRSI / ACI 315 placing drawings | AISC shop drawings (aisc.org) |
| Error mode | Wrong factor smears across tonnage | Missed piece is a discrete, findable hole |
The per-ton gap surprises people outside the trades: fabricated structural steel costs multiples of placed rebar per ton because each structural piece is cut, coped, drilled, welded, and painted individually, while rebar is bent in bulk on automated benders.
Do rebar and structural steel use the same drawings and tools?
No, and this is where cross-over attempts go wrong. The drawings barely overlap: rebar estimators live in the foundation and concrete sheets (S-100s and the concrete details); structural steel estimators live in the framing plans and steel details (S-200s and up, typically). On many jobs the only shared sheets are the foundation plans where anchor rods and embeds appear.
The tools split the same way. Rebar takeoff software is built around bar schedules, bend shapes (ACI standard hooks), lap tables, and placing-drawing output. Structural steel takeoff tools are built around member designations, section catalogs, piece counting, and BOM export — turning drawings into a bill of materials a shop can buy from. Pointing one at the other's drawings produces confident nonsense: a rebar tool doesn't know a W16X31 from a window tag, and a steel tool has no concept of a lap splice.
People split too. Rebar estimating rewards fluency in concrete detailing, ACI hook geometry, and factor discipline; structural estimating rewards section-catalog fluency, connection judgment, and exhaustive label-hunting. Shops that make one estimator do both across trades usually get one trade done well.
For the structural side of that split, SteelFlo is a Division 5 tool, deliberately: it reads structural and miscellaneous steel drawings, finds every member designation on every page, and draws a bounding box around each one so the piece count is visible and verifiable on the drawing — the count is the number of boxes, nothing inferred. Weights come from a library of 4,500+ sections across 6 standards, and with human verification of flagged detections, accuracy runs 95–99%. It does not do rebar takeoffs — bar schedules and bending lists are a different problem, and pretending otherwise is how tools end up mediocre at both.
Who hires which estimator?
Quick orientation if you're staffing or job-hunting:
- Rebar estimators work for reinforcing fabricators, rebar placing subs, and big concrete contractors. Deliverable: tonnage, accessories, and placing labor.
- Structural steel estimators work for steel fabricators and erectors. Deliverable: piece-level BOM, fab hours, coatings, erection. What the day-to-day looks like is in what does a steel estimator do?
- GC estimators need conversational fluency in both — enough to check a sub's tonnage against benchmarks, not enough to produce either takeoff from scratch.
Quick answers
Is rebar Division 3 or Division 5? Division 3 — concrete reinforcing, spec section 03 21 00. Structural steel is Division 5, section 05 12 00.
What units is a rebar takeoff in? Tons, computed from bar schedules with lap (5–15%) and waste (2–5%) factors, plus accessories counted separately.
What units is a structural steel takeoff in? Pieces first — every member counted — then tons via each section's catalog weight per foot.
Does SteelFlo do rebar takeoffs? No. SteelFlo is built for structural and miscellaneous steel (Division 5) — piece counting from member designations with verifiable boxes on the drawing.
Who supplies anchor bolts and embeds? Typically the steel fabricator furnishes them and the concrete contractor sets them — but confirm it in writing on every job.
Doing the Division 5 side? Upload a drawing set to SteelFlo and get every member counted and boxed for review, or start with the free steel weight calculator and the full section database at /shapes.