How Does the Metal Weight Calculator Work?
The calculator finds the volume of the section in cm³ and multiplies it by the density. Weight = volume × density. Dimensions are in mm, density is in g/cm³ and the result is in kg. It supports steel (7.85), cast iron (7.2) and aluminium (2.7).
Steel Weight Formulas for Each Shape
| Shape | Enter (mm) | Weight formula |
|---|---|---|
| Round bar | Diameter d, length L | π × (d ÷ 2)² × L × ρ |
| Square bar | Side a, length L | a² × L × ρ |
| Hex bar | Across flats AF, length L | (√3 ÷ 2) × AF² × L × ρ |
| Rectangle bar | Length L, width w, thickness t | L × w × t × ρ |
| Sheet / plate | Length L, width w, thickness t | L × w × t × ρ |
ρ is the density. In the calculator, convert mm to cm before you multiply (divide by 10), then divide grams by 1,000 for kg. The calculator does this for you.
Steel Round Bar Weight Formula and Worked Example
Take a steel round bar, Ø 50 mm and 1 m (1,000 mm) long. Area = π × 2.5² cm = 19.63 cm². Volume = 19.63 × 100 cm = 1,963.5 cm³. Weight = 1,963.5 × 7.85 = 15,413 g, which is 15.41 kg. The shortcut for steel round bar is kg per metre = d² ÷ 162, here 2,500 ÷ 162 = 15.4 kg.
More Worked Examples
- Square bar, 25 mm side, 1 m, steel: 2.5² × 100 × 7.85 = 4,906 g = 4.91 kg.
- Hex bar, 24 mm AF, 1 m, steel: 0.866 × 2.4² × 100 × 7.85 = 3,916 g = 3.92 kg.
- Rectangle bar, 1,000 mm long, 50 mm wide, 6 mm thick, steel: 100 × 5 × 0.6 × 7.85 = 2,355 g = 2.36 kg.
- Sheet, 2,000 × 1,000 mm, 3 mm thick, steel: 200 × 100 × 0.3 × 7.85 = 47,100 g = 47.1 kg.
Steel Round Bar Weight Chart
| Diameter (mm) | Weight (kg per metre) | Metres per tonne |
|---|---|---|
| 10 | 0.62 | 1,622 |
| 16 | 1.58 | 634 |
| 20 | 2.47 | 406 |
| 25 | 3.85 | 260 |
| 32 | 6.31 | 158 |
| 40 | 9.86 | 101 |
| 50 | 15.41 | 65 |
| 63 | 24.47 | 41 |
| 80 | 39.46 | 25 |
| 100 | 61.65 | 16 |
Values use a density of 7.85 g/cm³. They are theoretical weights. Real bars vary within the size tolerance.
Steel Products We Supply by Weight
Common Questions
How do you calculate the weight of a steel round bar?
Multiply the cross-section area by the length and by the density. For steel, weight in kg per metre is the diameter in mm squared, divided by 162. A Ø 50 mm bar weighs 2,500 ÷ 162 = about 15.4 kg per metre.
What density does the steel weight calculator use?
It uses 7.85 g/cm³ for steel, 7.2 g/cm³ for cast iron and 2.7 g/cm³ for aluminium. These are nominal values. Stainless and alloy steels differ slightly.
How do you find the number of bars in a tonne?
Divide 1,000 kg by the weight of one bar. A Ø 50 mm bar of 6 m weighs about 92.5 kg, so a tonne holds about 10.8 bars.
Is calculated weight the same as the weight on the invoice?
Calculated, or theoretical, weight is close but not identical. Real bars vary within the size tolerance, and weighed lots can differ by a small margin. Use the calculator to plan and quote, and confirm against the weighed quantity.