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How to calculate the weight of steel sheet, bars and pipes (formulas with examples)
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Short answer
Every steel weight formula comes from its density of 7850 kg/m³. Sheet weight in kg = length (m) × width (m) × thickness (mm) × 7.85; solid round bar per metre = diameter² (mm) × 0.00617; round pipe per metre = (outside diameter − wall) × wall × 0.02466.
The basis: steel density
A cubic metre of carbon steel weighs about 7850 kg. Converting units to millimetres and metres gives the factor 7.85 for plates and 0.00785 for sections per running metre. Every formula below is derived from that number.
| Shape | Formula | Example |
|---|---|---|
| Sheet (kg) | L m × W m × t mm × 7.85 | 6 × 1.25 × 3 × 7.85 = 176.6 kg |
| Solid round bar | d² × 0.00617 | 16 mm: 1.58 kg/m |
| Round pipe | (OD − t) × t × 0.02466 | 60.3 × 3.2: about 4.51 kg/m |
| Square or rectangular tube (approx.) | (2 × (a + b) − 4t) × t × 0.00785 | 100 × 100 × 4: about 12.1 kg/m |
| Flat bar | w × t × 0.00785 | 50 × 5: about 1.96 kg/m |
| Equal angle (approx.) | (2a − t) × t × 0.00785 | 50 × 50 × 5: about 3.73 kg/m |
The tube and angle formulas ignore corner radii, so results run slightly above standard tables. For IPE, HEA, HEB and UPN beams use the mass listed in the section tables directly.
From weight per metre to order weight
- Get the weight per metre from the formula or table
- Multiply by the piece length (usually 6 or 12 m)
- Multiply by the number of pieces and divide by 1000 for tonnes
FAQ
Why can actual weight differ from the calculated one?
Standards allow tolerances on thickness and dimensions, so actual weight can be slightly higher or lower. When supply is by weight, the weighbridge figure applies.
Do these formulas work for galvanized sheet?
Yes, as an estimate. The zinc coating adds a little weight depending on the coating mass.
General guidance — not an offer or commitment by BUILDORA.