Rectangular Tube Weight Calculation Formula
Accurate Engineering Weight Calculator & Comprehensive Guide
The wider side of the rectangular cross-section.
Enter a valid width.
The narrower side of the rectangular cross-section.
Enter a valid height.
Thickness of the tube wall. Must be less than half of width/height.
Thickness too large for dimensions.
Total length of the tube.
Enter a valid length.
Steel (Mild) – 7850 kg/m³
Aluminum (6061) – 2700 kg/m³
Stainless Steel (304) – 7900 kg/m³
Brass – 8500 kg/m³
Copper – 8960 kg/m³
Titanium – 4500 kg/m³
Custom Density…
Standard steel is ~7850.
Number of tubes needed.
Total Weight
0.00 kg
(0.00 lbs)
Weight Per Meter
0.00 kg/m
Cross-Sectional Area
0.00 mm²
Total Volume
0.00 m³
Formula Used: Weight = (Areaouter – Areainner) × Length × Density
Where Areaouter = Width × Height and Areainner = (Width – 2t) × (Height – 2t).
Where Areaouter = Width × Height and Areainner = (Width – 2t) × (Height – 2t).
Material Comparison Analysis
Comparing your specified geometry across common metals.
What is the Rectangular Tube Weight Calculation Formula?
The rectangular tube weight calculation formula is a mathematical method used by engineers, fabricators, and cost estimators to determine the theoretical mass of hollow structural sections (HSS). Unlike solid bars, rectangular tubes offer high strength-to-weight ratios, making accurate weight calculation critical for structural integrity, shipping logistics, and material costing.
This calculation determines the volume of material in the tube's wall and multiplies it by the specific density of the material (e.g., steel, aluminum, or stainless steel). While simple in concept, precision is required regarding wall thickness and dimensional tolerances.
The Formula and Mathematical Explanation
To calculate the weight of a rectangular tube manually, you must first determine the cross-sectional area of the metal wall, then multiply by the length and the material density. The standard rectangular tube weight calculation formula is derived as follows:
Weight (M) = [ (A × B) – (a × b) ] × L × ρ
Where:
- A = Outer Width (mm)
- B = Outer Height (mm)
- a = Inner Width = A – 2t (mm)
- b = Inner Height = B – 2t (mm)
- t = Wall Thickness (mm)
- L = Length (m)
- ρ = Density (kg/m³) – Note: Unit conversion required
Variable Definition Table
| Variable | Meaning | Typical Unit | Standard Value Range |
|---|---|---|---|
| A / B | Outer Dimensions | Millimeters (mm) | 20mm to 400mm+ |
| t | Wall Thickness | Millimeters (mm) | 1.0mm to 20mm |
| ρ (Rho) | Material Density | kg/m³ | Steel: ~7850, Alum: ~2700 |
| M | Mass/Weight | Kilograms (kg) | Calculated Result |
Practical Examples (Real-World Use Cases)
Example 1: Structural Steel Column
An engineer needs to calculate the weight of a mild steel RHS (Rectangular Hollow Section) for a building support.
- Dimensions: 100mm (W) x 50mm (H)
- Thickness: 4mm
- Length: 3 meters
- Material: Mild Steel (Density: 7850 kg/m³)
Step 1: Calculate Areas
Outer Area = 100 × 50 = 5000 mm²
Inner Width = 100 – (2×4) = 92 mm
Inner Height = 50 – (2×4) = 42 mm
Inner Area = 92 × 42 = 3864 mm²
Step 2: Cross-Sectional Area
Area = 5000 – 3864 = 1136 mm²
Step 3: Volume & Weight
Volume = 1136 mm² × 3000 mm = 3,408,000 mm³ = 0.003408 m³
Weight = 0.003408 m³ × 7850 kg/m³ = 26.75 kg
Example 2: Aluminum Framing
A fabricator is building a lightweight frame using 6061 Aluminum.
- Dimensions: 40mm x 20mm
- Thickness: 2mm
- Length: 6 meters
- Material: Aluminum (Density: 2700 kg/m³)
Using the tool above, the calculated weight per meter is approx 0.605 kg/m. For a 6m length, the total weight is 3.63 kg. This highlights why aluminum is preferred for lightweight applications despite being more expensive than steel.
How to Use This Rectangular Tube Weight Calculator
- Enter Dimensions: Input the outer width and height in millimeters. Ensure you measure the exterior of the tube.
- Specify Thickness: Input the wall thickness. Note: The calculator will validate that the thickness is physically possible (must be less than half the width/height).
- Select Material: Choose from standard presets like Steel, Aluminum, or Stainless Steel. The density will update automatically.
- Review Results: The tool instantly calculates the weight per meter and total weight.
- Analyze the Chart: Use the comparison chart to see how your tube compares to other material options in terms of weight.
Key Factors That Affect Rectangular Tube Weight
When applying the rectangular tube weight calculation formula, several real-world factors can influence the final figures:
- Corner Radius: Real-world tubes (RHS) have rounded corners, not sharp 90-degree angles. This removes a small amount of material, meaning the actual weight is often 1-3% lighter than the theoretical "sharp corner" calculation.
- Manufacturing Tolerances: Standards like ASTM A500 or EN 10219 allow for thickness variations (often +/- 10%). A tube sold as "3mm wall" might actually be 2.8mm or 3.1mm, affecting total weight significantly over long runs.
- Material Density Variations: "Steel" is not a single density. Mild steel is ~7850 kg/m³, while specific alloys might be slightly denser. Always check the mill test certificate for exact density.
- Galvanization/Coating: If the tube is galvanized, paint, or powder-coated, this adds surface weight that the basic geometric formula does not account for. Zinc coating can add 300-600g/m² of surface area.
- Cut Length Precision: While the formula assumes exact lengths (e.g., 6.000m), saw cutting removes material (kerf width), and supplier tolerances might mean you receive 6.050m lengths.
- Temperature: While negligible for weight, thermal expansion affects dimensions. Measurements taken in extreme heat may differ slightly from standard temperature measurements.
Frequently Asked Questions (FAQ)
What is the standard density of steel for tube calculations?
The industry standard density for carbon steel is 7850 kg/m³ (0.2836 lbs/in³). Stainless steel is typically heavier at roughly 7900-8000 kg/m³.
Does this formula account for rounded corners?
The basic formula assumes sharp corners (theoretical weight). To account for corner radii, engineering standards often apply a reduction factor or a more complex formula involving Pi, but the difference is usually negligible for general shipping estimation.
Why is my actual tube lighter than the calculated weight?
This is common due to "rolling tolerances." Manufacturers often produce tubes at the lower limit of the allowable thickness tolerance to save material costs while still meeting the specification standard.
How do I convert kg/m to lbs/ft?
To convert kg/m to lbs/ft, multiply by 0.6719. For example, a 10 kg/m tube weighs approximately 6.72 lbs/ft.
Can I calculate weight for square tubes with this?
Yes. For square tubes (SHS), simply enter the same value for both the "Outer Width" and "Outer Height" fields.
Is the wall thickness constant?
The formula assumes a constant uniform wall thickness. In reality, the weld seam area might be slightly thicker, and corners slightly thinner due to cold forming.
What if I have a hollow bar with very thick walls?
The formula remains valid as long as 2x thickness is less than the outer dimensions. If thickness equals half the width, it becomes a solid bar in that dimension.
How accurate is this for shipping logistics?
This calculation is highly accurate for theoretical weight. For shipping, it is recommended to add a 5% safety margin for dunnage, packaging, and manufacturing tolerances.
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