Structural Steel Takeoff Guide: Tonnage, Connections, Bolts, and Deck

A structural steel takeoff is the weight and count of every piece of steel on a building, from wide-flange beams to deck sheets and bolts. This guide walks through the full process in plain language, with real shape names, connection math, and the shortcuts a good estimator uses every day.

On This Page

1. What a Steel Takeoff Is

A structural steel takeoff is the full inventory of the steel on a building. Unlike concrete, which is sold by volume, steel is sold by weight - almost always in tons (2,000 lbs per ton). So the goal of the takeoff is to end up with a total tonnage number, plus counts of deck, bolts, studs, and connection material.

The takeoff feeds three buckets on the bid: main steel (columns and beams), secondary steel (joists, purlins, girts), and deck plus accessories (metal deck, headed studs, bolts, welds).

Why tonnage matters so much

Steel fabricators and erectors often price work per ton. A quoted number like $4,800 per ton installed includes fabrication, paint, delivery, and erection. If your tonnage is 5% off, your bid is 5% off. Everything rides on getting the weight right.

2. Understanding Shapes

The American Institute of Steel Construction (AISC) publishes a Shapes Database listing every standard rolled shape, its dimensions, and its weight per foot. If you have ever seen a drawing callout like W12x26 or HSS6x6x1/4, that is a shape from the AISC Manual.

Common shape prefixes

Weight per foot lookup

Every shape has a published weight per foot. You can memorize the common ones (a W12x26 weighs 26 lbs/ft by definition) or pull from the AISC Manual. Estimators usually keep a spreadsheet of the shapes they see most often.

3. Reading the Plans

Structural drawings are labeled S-1, S-2, and so on. For steel, the important sheets are:

Start with the column schedule

Columns are the backbone. Get them counted and weighted first. A typical column schedule shows the column mark (C1, C2), the shape (W14x90), height lifts, and base plate. Multiply shape weight by height, then by count, to get column tonnage.

Watch out: columns often change shape between floors. A column might be W14x90 in lift 1 (ground to level 3) and W14x61 in lift 2 (level 3 to roof). Each lift is a separate line.

4. Calculating Tonnage

Tonnage math is simple. You just need to stay organized.

The formula

Tons = (Linear Feet x Weight per Foot) / 2,000

Example: 100 linear feet of W12x26 = 100 x 26 = 2,600 lbs = 1.3 tons. Do this for every shape on every plan.

Beam-by-beam takeoff

Most estimators use a spreadsheet or takeoff software. Rows are beams, columns are shape, length, and weight. Software like PILRS or On-Screen Takeoff lets you click along a beam on the PDF and it measures automatically.

Do not forget

5. Connections and Bolts

Connections are where beams meet columns or other beams. They are made up of clip angles, shear tabs, stiffeners, and bolts. Connection weight is rarely drawn to scale. Instead, fabricators add a percentage to main steel tonnage.

Connection weight percentages

Bolts

High-strength bolts come in two grades: A325 (most common) and A490 (higher strength). Sizes are 3/4, 7/8, and 1 inch diameter in most commercial work. A typical simple shear tab uses 2-4 bolts; a moment connection can use 8-16.

For a preliminary bolt count, use 1-2% of main steel tonnage expressed as bolt weight. For a detailed takeoff, count the bolts on each connection type from the details and multiply by connection quantity.

6. Metal Deck and Joists

Metal deck

Metal deck is the corrugated steel sheet that spans between beams and supports the floor slab or roofing. Common types:

Takeoff is simple: measure square feet of each deck area on the framing plan, multiply by 1.05-1.10 for laps and waste, specify gauge (16, 18, 20, 22) and finish (galvanized, primed, painted).

Headed studs (shear connectors)

Composite deck floors need headed shear studs welded to the top flange of beams. Count from the plan and multiply stud count per beam by total number of similar beams. Typical stud is 3/4 inch diameter, 4 to 6 inches long.

Steel joists

Joists are listed on a joist schedule by designation like 24K9 or 32LH08. K-series are open-web joists, LH are long-span joists, DLH are deep long-span. Weight per foot comes from the Steel Joist Institute (SJI) catalog. Count joists per bay and multiply by span length and weight per foot.

7. Miscellaneous Metals

Miscellaneous metals (often called misc metals or M-metals) is the grab bag of smaller steel items. On most projects this is a separate spec section (05 50 00) and may be bid by a different contractor than structural steel.

Typical items

How to take off misc

Count each item from the architectural and structural details. Price stairs per riser or per flight (a typical commercial stair flight runs $4,500-$8,000 installed). Price railings per linear foot. Keep a catalog of historical unit prices so you can bid fast.

8. AI Structural Steel Takeoff

Steel takeoff used to mean hours of clicking beams with a digital pen. Not anymore.

What PILRS does

Review, do not rubber-stamp

AI handles the mechanical work. A senior estimator reviews the output for things like non-standard details, special coatings, and bid-day scope clarifications. The time savings goes straight to margin.

Frequently Asked Questions

How do you calculate structural steel tonnage from drawings?
Read the member schedule for each shape (like W12x26), measure the total linear feet of that member on the framing plan, multiply linear feet by the weight per foot (26 lbs/ft for a W12x26), and divide by 2,000 to get tons. Do this for every beam, column, brace, and girt, then add 8-12% for connections.
What does a shape like W12x26 mean on a steel plan?
W means wide flange (I-beam shape), 12 is the nominal depth in inches, and 26 is the weight in pounds per linear foot. So a W12x26 is a 12-inch wide flange that weighs 26 lbs per foot. The W, HP, S, C, MC, L, HSS, and Pipe prefixes each point to a different shape in the AISC Manual.
How long does a structural steel takeoff take?
A manual steel takeoff on a 50,000 sq ft building can take 20-40 hours when you count columns, beams, joists, deck, and connections. AI structural steel takeoff tools like PILRS typically produce the same tonnage report in 30-90 minutes with an estimator reviewing the output.
How do you count bolts on a structural steel takeoff?
Bolt counts come from typical connection details. A simple shear tab may use 2-4 bolts, a moment connection 8-16 bolts. Count each connection type, multiply by bolts per connection, and add 3-5% for waste and misdrives. For preliminary bids, use 1-2% of the steel tonnage as bolt weight.
How do you take off metal deck quantities?
Measure the square footage of each deck area on the framing plan. Multiply by 1.05-1.10 to cover side laps and end laps (deck is sold in sheets, not cut to size). Specify gauge, depth (1.5 inch B-deck, 3 inch N-deck), and finish. A 50,000 sq ft floor with 3 inch composite deck needs roughly 55,000 sq ft of ordered deck.
What is the difference between main steel and miscellaneous steel?
Main steel (structural steel) is the columns, beams, braces, and girders that carry gravity and lateral loads. Miscellaneous steel (misc metals) covers stairs, railings, ladders, lintels, embed plates, and support angles. They are often bid separately because fabrication and erection methods differ.
How do you read a steel framing plan?
Start at the column schedule to get column sizes by grid. Each beam on the plan has a callout showing the shape (W12x26) and any reaction or camber notes. Look for joist tags (K-series, LH-series) in the joist schedule. Elevations and sections show connection types. Always cross-check with the spec section 05 12 00.
What waste factor should I use on a steel takeoff?
Most steel fabricators add 2-5% for mill tolerance and cutting drops. Connections (plates, angles, stiffeners) add another 8-12% on top of main steel weight. Field erection bolts need 3-5% extra. Metal deck runs 5-10% for laps and cuts around penetrations.
How do you figure tonnage of steel joists (bar joists)?
Joists are priced by weight per foot from the SJI (Steel Joist Institute) catalog. A 24K9 joist weighs about 12 lbs/ft, a 32LH08 weighs about 17 lbs/ft. Count joist count per bay, multiply by span length and weight per foot. Bridging is additional and usually runs 2-4% of joist weight.
How do AI structural steel takeoff tools identify members?
AI steel takeoff software like PILRS reads the plan PDF, identifies column and beam tags using OCR, looks up shapes in the AISC database, measures linear feet along each member, and builds a tonnage table. It also reads schedules and connection details to auto-generate a bill of material for pricing and fabrication.
What is the difference between AISC Certified and non-certified steel fabricators?
AISC Certification (Building, Bridge, or Complex categories) means the fabricator has passed an independent quality program audit. Many commercial and public projects require it in the spec. Certified shops usually run 3-8% higher cost but reduce inspection overhead and defects, which is why owners often specify them.
How do you handle shop drawings vs. design drawings in takeoff?
Bid off the design drawings (structural engineer's issued-for-construction set). Shop drawings come later and reflect the fabricator's interpretation. If shop drawings are available during re-estimate or change order review, use them because they include actual bolt counts, plate sizes, and welds to 1/16 inch accuracy.

Run Your First Structural Steel Takeoff Free

No credit card. No setup call. Upload a plan set and see the output in minutes.

Start Free Takeoff Back to Structural Steel