Metal Weight Calculator — Bar, Plate, Pipe, Hex, and Angle in All Alloys

Calculate the weight of common metal sections — round bar, flat plate or sheet, hollow pipe or tube, square bar, hexagonal bar, and equal leg structural angle — in any engineering alloy. Select the shape, enter dimensions in millimetres or inches, choose the alloy, and the calculator returns weight per piece, total weight for a specified quantity, and weight per unit length. A full step-by-step formula breakdown is shown for every calculation so you can verify the result or reproduce it in your own spreadsheet.

How Metal Weight Is Calculated

The fundamental relationship is simple: weight equals volume multiplied by density. The engineering challenge lies in computing the cross-sectional area accurately for each section type, ensuring consistent units, and applying the correct alloy density. All six formulas used by the calculator above are derived from first principles as follows:

Round Bar / Rod

Cross-sectional area  A = π/4 × D²
Volume (mm³)            = A × L = π/4 × D² × L
Weight (kg)             = A × L × ρ / 10⁶   (ρ in g/cm³, dims in mm)

Shortcut for steel (ρ = 7.85 g/cm³):
  W (kg/m) = 0.00617 × D²   (D in mm)

Example: D = 50 mm, L = 3,000 mm, carbon steel:
  A   = π/4 × 50² = 1,963.5 mm²
  V   = 1,963.5 × 3,000 = 5,890,486 mm³ = 5,890.5 cm³
  W   = 5,890.5 × 7.85 / 1,000 = 46.24 kg

Hollow Pipe or Tube (OD and Wall Thickness)

ID = OD − 2 × WT
Area  A = π/4 × (OD² − ID²)

Shortcut for steel pipe:
  W (kg/m) = 0.02466 × WT × (OD − WT)   (OD, WT in mm)

Example: OD = 114.3 mm, WT = 6.02 mm (4-in Sch 40), L = 6,000 mm:
  ID  = 114.3 − 12.04 = 102.26 mm
  A   = π/4 × (114.3² − 102.26²) = π/4 × (13,064.5 − 10,457.1) = 2,044.4 mm²
  W   = 2,044.4 × 6,000 × 7.85 / 10⁶ = 96.29 kg

Flat Plate or Sheet

Area  A = Width × Thickness
W (kg) = W × T × L × ρ / 10⁶

Shortcut for steel plate:
  W (kg/m²) = 7.85 × T   (T in mm)   → 1 mm plate ≈ 7.85 kg/m²

Example: 1,500 × 3,000 mm × 10 mm plate, carbon steel:
  V   = 1,500 × 3,000 × 10 = 45,000,000 mm³ = 45,000 cm³
  W   = 45,000 × 7.85 / 1,000 = 353.25 kg

Hexagonal Bar (Across-Flats)

Area  A = (√3/2) × AF² = 0.86603 × AF²
Across-corners AC = AF × 2/√3 = AF × 1.15470

Shortcut for steel hex bar:
  W (kg/m) = 0.006798 × AF²   (AF in mm)

Example: AF = 41 mm (common stock size), L = 3,000 mm:
  A   = 0.86603 × 41² = 0.86603 × 1,681 = 1,455.6 mm²
  W   = 1,455.6 × 3,000 × 7.85 / 10⁶ = 34.28 kg

Equal Leg Angle

Area  A = T × (2A − T)   (equal leg A×A×T)
  The corner material is counted once: one leg = A×T, other leg = (A−T)×T
  Total = A×T + (A−T)×T = T×(2A − T)

Example: 75×75×8 mm, L = 6,000 mm, steel:
  A   = 8 × (150 − 8) = 8 × 142 = 1,136 mm²
  W   = 1,136 × 6,000 × 7.85 / 10⁶ = 53.51 kg
  kg/m = 1,136 × 7.85 / 1,000 = 8.92 kg/m  (matches EN 10056 tables)

Alloy Density Reference Table

The densities used in the calculator are the accepted nominal values from the relevant material standards and ASM Handbook data. For most engineering purposes — procurement, transport, load calculations, structural design — these values are sufficient. Use the certified material density from the mill certificate if the calculation is for high-value alloy procurement by weight or for precision mass-properties calculations.

Standard Section Weight Tables: Steel Round Bar, Pipe, and Plate

Round Bar — Carbon Steel (kg/m)

Flat Plate — Carbon Steel (kg/m²)

Practical Guidance: Applying Section Weights in Engineering

Pipe Weight and ASME Schedule Correlation

In piping engineering, pipe weight per unit length determines support span design, flange face loading, and transport logistics. ASME B36.10 (welded and seamless wrought steel pipe) and B36.19 (stainless steel pipe) tabulate nominal pipe size (NPS), outside diameter, and wall thickness for each schedule. The OD is fixed for a given NPS; wall thickness varies with schedule number. To compute weight using this calculator, enter the OD and wall thickness from the relevant schedule table. Note that ASME dimensions are in inches — use the inch input mode or convert: 1 inch = 25.4 mm.

For corrosion allowance design in piping systems, the specified minimum wall thickness (SMYS) is the pressure-design wall thickness plus corrosion allowance. When calculating pipe weight for support design, use the nominal (ordered) wall thickness, not the minimum thickness. Pipe is typically ordered to a nominal wall thickness with an undertolerance of 12.5% per ASTM A53/A106/ASME B36.10.

Density Correction for Temperature

Metals expand on heating, reducing density. The thermal expansion coefficient for carbon steel is approximately 12 × 10⁻⁶ /°C, giving a volume change of approximately 0.36% at 300°C. For most practical weight calculations this is negligible, but for high-temperature pressure vessel design to ASME code (where allowable stresses are temperature-dependent), always verify whether the code table uses density at 20°C or at the design temperature. The annealing and normalising guide discusses volume changes during phase transformations, which can be significantly larger than thermal expansion effects.

Weight vs. Mass: Units for Procurement

In engineering, weight and mass are often used interchangeably. Strictly, weight is a force (Newtons) and mass is a quantity (kilograms). For metal procurement, the quantity traded is always mass in kilograms or tonnes (metric). Steel is typically priced per tonne (1,000 kg). Aluminium, titanium, and nickel alloys are often priced per kilogram due to their higher unit value. For conversion: 1 metric tonne = 1,000 kg = 2,204.6 lb = 1.1023 short tons. For pipe and bar, weight per unit length (kg/m or lb/ft) is used for stock management and crane lifting calculations.

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