Warehouse Steel Takeoff Calculator

Purpose and model boundary

This calculator takes off the steel of a building frame drawn on the page, such as a warehouse, a shed or a canopy: main frames of columns and rafters under a gable or single-slope roof, purlins and eave struts, side and end wall girts, and wall and roof bracing, with each wall clad, open or set against an existing building. It counts the members drawn and gives each member's length, its section's idealized area and, when you enter a density, its weight. It then gives the count, length and weight by member type, by section and by group, and the totals in pounds and short tons or kilograms and tonnes, for up to 1,000 members. Optionally it prices the steel and the roofing and cladding sheets at rates you type.

It is an arithmetic takeoff of the members drawn, for estimating and learning. It is not a structural design, a fabrication bill of materials or a supplier quote.

The spreadsheet is the calculation authority. The page sends the drawn geometry, the sections table and the values you type to the workbook and shows only what the workbook returns.

Inputs and units

• The drawing. Frame lines, width, eaves, ridge or single slope, purlin and girt spacings and braced bays are drawn on the canvas, in the Plan, Front, Back, Left, Right and 3D views. The canvas sends the model's nodes (x along the building, y across it, z up, in feet or metres), its members (start and end node, section, group and type), its member groups, and the net roof and wall areas it measures (along the slope, less any openings; an open wall sends none).
• Sections. Up to 12 rows in the calculator panel: a name, the profile (I, C, L, HSS, PIPE or RECT) and the dimensions that profile uses, in inches (US) or millimetres (Metric), and optionally the section's own steel price. Sections are assigned to members on the canvas.
• Density (optional) of the material every member is made of, in lb/ft³ or kg/m³. Left blank, the takeoff gives lengths and areas without weights.
• Prices (optional): a steel price per pound or per kilogram, used for every section without a price of its own, and roofing and cladding sheet prices per square foot or per square metre.
• Units: US (feet, inches, pounds) or Metric (metres, millimetres, kilograms).

Governing relationships

• Each member's length is the distance between its two end nodes.
• Each section's area is that of its idealized, sharp-corner outline, as the sum of its parts: I and C, 2·bf·tf + (d − 2·tf)·tw; L, t·(b + d − t); HSS, 2·t·(b + d − 2·t); pipe, π·t·(od − t); rectangle, b·d. Ix and Iy are about the centroidal axes, x horizontal and y vertical as drawn; a channel's and an angle's centroid is found from its parts, and an angle's axes are the ones parallel to its legs.
• Each member's weight is its length times its section's area times the density. The totals are in pounds and short tons of 2,000 lb, or kilograms and tonnes of 1,000 kg.
• The estimate prices each section's weight at its own price, else the steel price, the roof area at the roofing price and the wall area at the cladding price, and adds up the parts that are priced.

Calculation sequence

1. The workbook checks the node, section, member, group and panel rows and the prices, and refuses the first row that is wrong.
2. It works out each member's length from its two end nodes, and each section's area, Ix and Iy from its dimensions.
3. With a density, it works out each member's weight and each section's weight per length.
4. It adds the members up by type (in the order the types first appear), by section and by group, and gives the totals.
5. With prices, it works out the steel, roofing and cladding estimate from the section weights and the net roof and wall areas the canvas sends.

Outputs and interpretation

• By member: each member's length, section area and weight, with its row status.
• By section: its area, its second moments Ix and Iy, its weight per foot or per metre, how many members use it with their total length and weight, and, when priced, the rate applied and their cost.
• By type and by group: the count, the total length and the total weight of the members of each. Members with no group are not listed under groups.
• Totals: the total length of every member, end node to end node, with no allowance for cutting, laps or waste; the total weight in pounds or kilograms and in short tons or tonnes; the net roof and wall areas.
• Estimate: the priced parts and their sum. A part without a price stays blank and the estimate note says why; with no price at all the note reads Not calculated: enter pricing.

Weights are blank until a density is entered.

Validation and status logic

The status reads OK when the drawing can be taken off. NOT VALID names the first node, section, member, group or panel row, or the price, to fix, and every number is then blank, while the member-by-member table still shows each row's status. CHECK flags member types that differ only in letter case: they are counted together under the first spelling.

Assumptions and limitations

Only the members drawn are counted: no connections, plates, bolts, welds, coatings, or cutting and waste allowance. Real rolled shapes have fillets and corner radii, so their published areas differ from the idealized outline's. The takeoff makes no strength, stability or capacity check. No price is a supplier bid or a current market rate.

Restrictions and non-computing states

• Up to 1,000 nodes, 1,000 members, 12 sections, 50 groups and 40 roof and wall panels; at most 20 member types.
• Node coordinates X, Y and Z are numbers between -5,000 and 5,000 ft.
• Section dimensions are between 0.0012 and 120 in, and the outline must be one that can exist.
• A density must be above zero and at most 1,600 lb/ft³.
• A section's price is a number of zero or more, at most $100 per lb; a money result above $1,000,000,000 is refused.
• A panel's surface is ROOF or WALL, with an area above zero and at most 1,000,000 ft².
• IDs must differ, compared without regard to letter case; an ID or label is at most 64 characters and holds none of * ? ~ < > =.
• Each member has a start and an end node in the node grid that are not the same node and not at the same point, and names a section in the sections grid and, if any, a group in the group grid.

Errors and warnings

A drawing the workbook cannot take off reads NOT VALID with the first row to fix, for example a member whose section is not in the sections table, two IDs that differ only in letter case, or an ID holding one of * ? ~ < > =. A CHECK status names the first spelling under which member types that differ only in letter case are counted together.

The method is an arithmetic takeoff of the members drawn. Each member's length is the distance between its end nodes. Each section's area is the sum of the rectangles, or the annulus, of its idealized sharp-corner outline, and its second moments Ix and Iy are found about the centroidal axes by the parallel-axis theorem. Each member's weight is its length times its area times the density you enter, totalled in pounds and short tons of 2,000 lb or in kilograms and tonnes of 1,000 kg. The full method is also stated on the workbook's References sheet.

Sources and further reading

• Centroids of composite areas, second moments of area and the parallel-axis theorem, used for each section's area, Ix and Iy: B. J. Goodno and J. M. Gere, Mechanics of Materials, 9th edition, Cengage Learning, 2018, appendix D, Review of Centroids and Moments of Inertia. Publisher page
• Conversion factors for the pound, the short ton, the kilogram and the metric ton, and for lengths and areas between US and SI units: A. Thompson and B. N. Taylor, Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 edition, appendix B, Conversion Factors. NIST
• The published dimensions and properties of rolled steel shapes, which include fillets and corner radii and so differ from the idealized outlines used here: American Institute of Steel Construction, Steel Construction Manual, 16th edition, 2023. AISC

No table, chart or text from a standard, manual or commercial publication is reproduced, and no section property comes from a shape table: every dimension and the density are entered by you or drawn on the canvas. None of the authors or publishers named here has reviewed or endorses this calculator.

The workbook was checked by two independent methods: a hand count from the building dimensions, and an independent script over the exported node and member model, including each section's area, Ix and Iy by its own split into parts. The two agree on every count exactly and on every length and section property to within rounding.

Applicable design codes and a qualified engineer govern real structures.