Hollow sections are square or rectangular tubes used for canopy frames, fences, railings, ceilings, and light structural work. Before buying, the most common question is: how much does a hollow section weigh per length? Weight drives both the price (steel is sold by the kilogram) and your project’s material take-off.
Hollow section weight formula
For square and rectangular hollow, theoretical weight is:
Weight (kg/m) = [2 × (a + b) − 4 × t] × t × 0.00785
where a and b are the outer sides (mm), t is the wall thickness (mm), and 0.00785 comes from steel density 7.85 g/cm³. For weight per length, multiply by the standard 6 m.
Hollow section weight table (popular sizes)
Theoretical weight in kg/m for the three most common wall thicknesses:
| Size (mm) | t = 1.5 mm | t = 2 mm | t = 3 mm |
|---|---|---|---|
| 20 × 20 | 0.87 | 1.13 | 1.60 |
| 20 × 40 | 1.34 | 1.76 | 2.54 |
| 25 × 25 | 1.11 | 1.44 | 2.07 |
| 30 × 30 | 1.34 | 1.76 | 2.54 |
| 40 × 40 | 1.81 | 2.39 | 3.49 |
| 40 × 60 | 2.28 | 3.01 | 4.43 |
| 40 × 80 | 2.76 | 3.64 | 5.37 |
| 50 × 50 | 2.28 | 3.01 | 4.43 |
| 50 × 100 | 3.46 | 4.58 | 6.78 |
| 60 × 60 | 2.76 | 3.64 | 5.37 |
| 75 × 75 | 3.46 | 4.58 | 6.78 |
| 100 × 100 | 4.64 | 6.15 | 9.14 |
Example: a 40 × 40 hollow at 2 mm wall = 2.39 kg/m × 6 m = 14.3 kg per length.
These are theoretical (sharp-corner) weights. Actual weight may be slightly lower due to corner radius and mill tolerance.
Black vs galvanized hollow
- Black hollow (SS400 / SPHT) — available 15×30 up to 250×250 mm, 1 to 6 mm thick. Best for frames that will be painted or used indoors.
- Galvanized hollow — zinc-coated (pre-galvanized), available 15×30 up to 60×60 mm, 0.7 to 1.7 mm thick. More corrosion-resistant for outdoor use.
The available thickness list for every size is on our hollow section product page.
Calculate automatically
Don’t want to do the maths? Use our steel weight calculator — enter the size and wall thickness and get weight per length instantly.
Need a hollow section price today?
Marselus Steel keeps black and galvanized hollow sections in ready stock at our Tipar Cakung warehouse, North Jakarta. Contact our team on WhatsApp for the latest quote and Greater Jakarta delivery.
