How to calculate the weight of sheet metal, pipes, and sections? Equations with examples

Last updated: October 18, 2026

The weight of any piece of iron = its volume × the density of iron, and the density of carbon steel is approximately 7850 kg/m³. From this rule, we can derive quick equations: the weight of sheet metal in kilograms = length (m) × width (m) × thickness (mm) × 7.85, the weight of a round pipe per meter = (outer diameter − thickness) × thickness × 0.02466, and the weight of reinforcing steel per meter = diameter² ÷ 162.

What is the basic rule for calculating the weight of iron?

Iron is a nearly homogeneous material, so the weight of any piece is determined solely by its volume. If you know the volume of the piece in cubic meters, multiply it by 7850 to get the weight in kilograms. However, volume in cubic meters is a small and cumbersome number for everyday calculations, so engineers and technicians convert the equation to practical units: lengths in meters and thicknesses in millimeters.

The concise rule from which all equations are derived: One linear meter of metal with a cross-sectional area of 1 mm² weighs 0.00785 kg. That is, you calculate the area of the metal in the cross-section in square millimeters, then multiply it by 0.00785 to get the weight in kilograms per meter, then multiply by the length.

This method is suitable for any sector: sheet metal, pipes, angles, flats, beams, and even custom-shaped pieces.

How do you calculate the weight of a sheet of iron?

The sheet metal is rectangular with a constant thickness, so the equation is straightforward:

Weight (kg) = Length (m) × Width (m) × Thickness (mm) × 7.85

The figure 7.85 represents the weight of one square meter of sheet metal with a thickness of 1 mm. This means that for every square meter of thickness, the weight increases by 7.85 kg.

Illustrative example: sheet metal

• A 1.25 x 2.5 meter slab with a thickness of 2 mm: 1.25 x 2.5 x 2 x 7.85 ≈ 49.1 kg.
• A 1 x 2 meter board with a thickness of 1.5 mm: 1 x 2 x 1.5 x 7.85 ≈ 23.6 kg.
• Base (plate) 200 × 200 mm with a thickness of 10 mm: 0.2 × 0.2 × 10 × 7.85 ≈ 3.1 kg.

For sheet metal components, such as cable trays or bent sections, calculate the sheet width before bending (the sum of the lengths of the straight sides) and then apply the same equation. This makes thickness a crucial factor in the weight of the cable tray, as explained in the article. Choosing the cable tray size, fill percentage, and weights.

How do you calculate the weight of a circular pipe?

The area of metal in a pipe cross-section is the difference between two circles, and after simplification the equation becomes:

Weight (kg/m) = (Outer Diameter − Thickness) × Thickness × 0.02466

Where the diameter and thickness are in millimeters. The number 0.02466 is the product of π (3.1416) × 0.00785.

Illustrative example: pipes

• A pipe with an outer diameter of 114.3 mm and a thickness of 4 mm: (114.3 − 4) × 4 × 0.02466 ≈ 10.9 kg/m, and a length of 6 meters weighing approximately 65.3 kg.
• 60.3 mm pipe with a thickness of 3 mm: (60.3 − 3) × 3 × 0.02466 ≈ 4.24 kg/m.

Note that pipes are sometimes labeled in inches (2 inches, 4 inches), but this is a nominal size and does not represent the actual outer diameter. Always use the actual outer diameter in millimeters from the supplier's chart.

How do you calculate the weight of square, rectangular, and angle pipes?

For a square pipe with an outer side a and a thickness t, the area of the metal is approximately 4 × t × (a − t), so the equation is:

Squared (kg/m²) = 4 × t × (a − t) × 0.00785

Rectangular a × b (kg/m) = 2 × t × (a + b − 2t) × 0.00785

Equilateral angle (kg/m) ≈ (2a − t) × t × 0.00785

Simplified (flat) with width w (kg/m) = w × t × 0.00785

Solid round iron with a diameter of d (kg/m) = d² × 0.00617

Illustrative example: Sectors

• Square 50 × 50 × 2 mm: 4 × 2 × 48 × 0.00785 ≈ 3.01 kg/m, and a length of 6 meters is approximately 18.1 kg.
• Square 100 × 100 × 4 mm: 4 × 4 × 96 × 0.00785 ≈ 12.1 kg/m.
• Rectangular 100 × 50 × 3 mm: 2 × 3 × (150 − 6) × 0.00785 ≈ 6.78 kg/m.
• Angle 50 × 50 × 5 mm: (100 − 5) × 5 × 0.00785 ≈ 3.73 kg/m.
• Simplified 50 × 5 mm: 50 × 5 × 0.00785 ≈ 1.96 kg/m.

These equations ignore the roundness of the corners in square pipes, so the actual weight in the manufacturers’ tables is slightly less than the output, a small difference that is sufficient for estimation in calculating the initial quantities.

How do you calculate the weight of reinforcing steel using the equation diameter² ÷ 162?

The reinforcing bar has an almost solid circular cross-section, so its weight per meter = d² × 0.00617. Since 1 ÷ 162 ≈ 0.00617, the common equation on websites is:

Weight per meter (kg) = Diameter (mm)² ÷ 162

To calculate the tonnage of reinforcement for a concrete element: add up the lengths for each diameter, multiply by the weight per meter, then add a percentage for overlaps (connections) and waste according to the details of the plans.

Summary of equations and tips for calculating quantities

Illustrative example: a small metal frame

A frame made of 8 square tubes (50 x 50 x 2 mm, each piece 3 meters long) with 4 sheet metal bases (200 x 200 x 10 mm). Figures are approximate.

1. Pipes: 8 x 3 = 24 meters x 3.01 ≈ 72.2 kg.
2. Bases: 4 x 3.1 ≈ 12.6 kg.
3. The theoretical total is about 85 kg, plus the weight of the bolts, welding, and zinc coating if the frame is galvanized.

Practical tips:

• Galvanizing adds weight: The zinc coating in hot-dip galvanizing adds a small percentage of weight, depending on the thickness and surface area of the workpiece. The differences between galvanizing methods are explained in the article. Hot-dip galvanizing or electro-galvanizing.
• Aluminum is about two-thirds lighter: Its density is about 2700 kg/m³, which is about 0.34 times the weight of iron of the same dimensions.
• Stainless steel is slightly heavier: Its density is in the range of 7900 to 8000 kg/m³ depending on the grade.
• Calculate the loss separately: The weight of the finished pieces does not equal the weight of the raw material purchased, as cutting slabs and lengths leaves residues.

Why is it important to calculate the weight before manufacturing?

Weight is not a number to be trifled with. It is the basis for several decisions in any mining project:

• Cost estimation: Iron is often priced by weight, so knowing the weight gives you a preliminary picture of the cost of materials before requesting bids.
• Structural loads: Solar panel structures on roofs, for example, add a load that the roof must bear, and the weight of the structure is part of this calculation.
• Transportation and lifting: The number of trucks and the type of crane depend on the total weight and the longest piece.
• Comparing the offers: Two offers with the same dimensions but very different weights often mean different thicknesses, so ask about the thickness before comparing.

And in MITS Metal Manufacturing Plant In Al-Kharj, the weights of the pieces are calculated from the plans before cutting and shaping, whether they are cable trays, panel structures, or Custom-made metal parts with CNC machiningThis helps the customer know the quantity and weight before implementation.

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