Steel tonnage calculator: pounds and tons by member

How steel tonnage is taken off

Structural steel is measured in linear feet per member and bought in short tons of 2,000 pounds, so every steel takeoff is a length to weight conversion. You work the structural framing plans (the S sheets) with the column schedule and the braced and moment frame elevations open, and you build a member list: designation, count, and length for every beam, girder, column, and brace. Nothing gets averaged across the frame. A W21x62 spandrel and a W12x26 infill beam are separate lines on the takeoff because they weigh very different amounts per foot.

What makes this arithmetic work is the AISC naming convention. On a rolled shape, the number after the x is the weight in pounds per linear foot, so a W21x62 weighs 62 pounds for every foot of it, straight or cambered, primed or bare. That one fact turns a scaled measurement into a purchase quantity. HSS and angle designations end in wall thickness or leg thickness instead of weight, so their pounds per foot come out of the published tables rather than out of the name. See wide flange beam for how W shape designations read.

Order of operations on a real bid: member list, then weight, then allowances, then price. Estimators who jump to dollars per ton before the allowances are in are the ones who lose money on braced frames.

The formulas

Linear feet per line = quantity x length in feet Weight per line = linear feet x pounds per foot Bare member weight = sum of every line Connection allowance = bare member weight x allowance percent / 100 Total weight = bare member weight + connection allowance Short tons = total weight / 2,000

Keep every designation on its own line rather than blending sizes. It costs nothing at takeoff and it is the only way to check a number later, or to reprice when the engineer upsizes a bay after the first plan revision.

Where the pounds per foot come from

• W shapes: the designation itself. The number after the x is pounds per linear foot, per the AISC naming convention, so W12x26 is 26 lb per ft and W36x160 is 160 lb per ft. The first number is a nominal depth, not an actual one, which matters for clearances but not for weight.
• HSS square and rectangular tube: nominal weights from the dimensions and properties tables in Part 1 of the AISC Steel Construction Manual, for ASTM A500 tube. HSS6x6x3/8 is 27.48 lb per ft, HSS8x8x1/2 is 48.85 lb per ft. Note that weight tracks perimeter and wall, so HSS6x4x1/4 and HSS5x5x1/4 both come out at 15.62 lb per ft.
• Angles: nominal weights from the angle table in the same part of the AISC Manual, for ASTM A36 material. L4x4x3/8 is 9.8 lb per ft, L6x4x3/8 is 12.3 lb per ft.
• Plate: steel weighs 490 pounds per cubic foot, which works out to 40.8 pounds per square foot per inch of thickness. That is the constant for pricing base plates, gussets, and shear tabs explicitly instead of inside a percentage.
• The ton: US commercial steel trades in short tons of 2,000 lb. A metric tonne is 2,204.6 lb, so quietly mixing the two moves a steel number by about 10 percent.

What the member schedule does not show

Bare shape weight is not the tonnage a fabricator bids, and this is where most first steel bids go wrong. The framing plan shows members. It does not show the connection material that holds them together: shear tabs, clip angles, end plates, stiffeners, doubler plates, gusset plates, cap plates, base plates, anchor rods, bolts, and weld metal. All of that is real steel, it is fabricated and shipped and erected, and at bid time you do not have the shop drawings that would let you weigh it piece by piece. So it is carried as a percentage of the member weight.

The percentage is estimator judgment, not a published constant, and it moves with connection type. Simple shear connected gravity framing sits at the low end, commonly in the 5 to 10 percent range. Moment frames, braced bays with heavy gussets, and trusses push well above 10 percent, because a single braced bay can carry gusset plates that weigh more than the brace they connect. A braced frame job and a simple span job are not comparable, so a single generic factor applied to both will be wrong twice.

The right way to set your number is your own history. Pull the approved shop drawing weights from finished jobs, compare them against the bid takeoff weight for the same frames, and keep the ratio by building type: warehouse gravity framing, mid rise composite floors, braced or moment framed work. That gives you a factor with your own detailer and your own fabricator behind it. Default 10 percent is a starting point for the first job, not an answer.

Two more things that live outside this number. Steel deck is measured in square feet and open web joists are typically quoted by the joist manufacturer, so neither belongs in the member tonnage. Miscellaneous metals such as stairs, rails, loose lintels, and embeds usually carry their own Division 05 line items, and a fabricator scope letter spells out what is in and out. Camber is the reverse case: it costs shop money per beam but adds no weight at all, so it never shows up in tonnage. For the wider definition and its pricing conventions see steel tonnage.

Worked example

Take the calculator defaults, a small framed structure with four member groups.

• 10 W21x62 girders at 40 ft each: 10 x 40 = 400 lf, and 400 x 62 = 24,800 lb
• 20 W12x26 infill beams at 30 ft each: 20 x 30 = 600 lf, and 600 x 26 = 15,600 lb
• 12 HSS6x6x3/8 tube columns at 14 ft each: 12 x 14 = 168 lf, and 168 x 27.48 = 4,616.64 lb, shown as 4,617 lb
• 10 L4x4x3/8 kickers at 12 ft each: 10 x 12 = 120 lf, and 120 x 9.8 = 1,176 lb

Total length is 400 + 600 + 168 + 120 = 1,288 linear feet. Bare member weight is 24,800 + 15,600 + 4,617 + 1,176 = 46,193 lb. At the default 10 percent connection allowance, that adds 4,619 lb, for a total of 50,812 lb. Divide by 2,000 and the frame is 25.41 short tons, which most estimators would carry as 25.5 tons after rounding up to the next tenth. The 1,288 linear feet and the 46,193 pounds are measurement. The 10 percent is judgment, and it should stay visible as its own line in the estimate so a reviewer can argue with it.

From tons to a priced line

Tonnage is the quantity half of a steel bid. The priced line applies per ton rates for material, shop fabrication, and field erection, sometimes as one combined rate and sometimes as three, plus the items that never price per ton at all: camber adders, galvanizing by the pound, AESS finish premiums, and crane and equipment time. For how those pieces come together into a submitted number, see the guide on how to bid structural steel as a subcontractor.

That is the step Ruh handles. It reads the drawing set, measures the scope member by member off the framing plans and schedules, and prices those measured quantities against the contractor's own price book, with every line traceable back to the sheet it came from. Your estimator reviews the member list, the allowances, and the rates before anything goes into the bid.