When a family orders a new main gate or a terrace shed, the fabricator's quote lists sizes like “40 × 40, 2 mm” and a total weight in kilos. Knowing the usual square tube size for gate, grill and shed work helps compare quotes and avoid paying for steel that never arrives. This guide covers the sizes workshops in Ludhiana, Rajkot and Coimbatore use most, with weights worked out.
Square tube size for gate, grill and shed
| Job | Frame | Infill / bars | Wall thickness |
|---|---|---|---|
| Window grill | 25 × 25 | 20 × 20 or 12 mm square bar | 1.6–2 mm |
| Balcony railing | 40 × 40 posts | 25 × 25 balusters | 2 mm |
| Main gate (single leaf, up to ~4 ft) | 40 × 40 or 50 × 50 | 25 × 25 | 2–2.6 mm |
| Large double gate | 50 × 50 or 60 × 60 | 25 × 25 or 32 × 32 | 2.6–3.2 mm |
| Terrace shed | 72 × 72 or 80 × 80 columns | 40 × 40 purlins | 3.2–4 mm |
These are common workshop choices, not design values. Sheds, mezzanines and anything carrying people or wind load should be sized by a structural engineer.
Weights you can check on site
| Size (mm) | kg per metre | kg per 6 m length |
|---|---|---|
| 20 × 20 × 1.6 | 0.92 | 5.5 |
| 25 × 25 × 2 | 1.44 | 8.7 |
| 40 × 40 × 2 | 2.39 | 14.3 |
| 50 × 50 × 2.9 | 4.29 | 25.7 |
| 72 × 72 × 3.2 | 6.91 | 41.5 |
Mill tables list slightly lower weights because real tubes have rounded corners. A big shortfall (10% or more) usually means a thinner wall than ordered.
Try the free Square Tube Weight Calculator
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Estimating the steel in a gate
Take a single-leaf gate 4 ft wide and 6 ft high (about 1.22 m × 1.83 m) with a 40 × 40 × 2 frame and vertical 25 × 25 × 2 bars every 4 inches.
Frame: 2 × (1.22 + 1.83) = 6.1 m × 2.39 kg/m ≈ 14.6 kg Bars: about 11 bars × 1.83 m = 20.1 m × 1.44 kg/m ≈ 29.0 kg Total steel ≈ 43.6 kg (+ about 5% for cutting waste ≈ 46 kg)
Hinges, locks, sheet panels and paint come on top. With the steel weight known, a fabricator's rate per kilo becomes easy to compare.
What does “18 gauge” or “16 gauge” mean in mm?
Shops still use gauge for thin sections. Roughly, 18 gauge is about 1.2 mm, 16 gauge about 1.6 mm and 14 gauge about 2 mm. Ask for the wall in millimetres on the bill to avoid ambiguity.
Buying checks
- Measure the wall at a cut end with a vernier caliper.
- Weigh one length: a 6 m 40 × 40 × 2 tube should be about 14 kg.
- Check for rust and dents, especially on stock that has been stored outdoors.
- Ask for primer before painting; red oxide or zinc-rich primer protects the inside corners.
The square tube weight calculator gives kg per metre, per piece and for a whole order in MS, stainless steel or aluminium, for any side and wall thickness.
Frequently asked questions
Which square tube size is best for a gate?
Commonly 40 × 40 or 50 × 50 mm for the frame with 25 × 25 mm bars, in 2–2.6 mm wall, for an ordinary house gate.
How much does a 40 × 40 × 2 mm square tube weigh?
About 2.39 kg per metre, or 14.3 kg per 6 m length (slightly less in mill tables).
How do I estimate the steel in a gate?
Add up the running metres of each tube size, multiply by its kg per metre, and add about 5% for waste.
What is 16 gauge in mm?
About 1.6 mm. Ask for thickness in millimetres on the bill.
What size tube is used for a terrace shed?
Often 72 × 72 or 80 × 80 mm columns with 40 × 40 purlins, but sheds should be designed by a structural engineer.
Keep reading
- Square Tube Weight Calculator: the free tool this guide explains.
- All construction calculators
- MS Pipe Size Chart: NB, OD and ID Explained for Buyers
Sources: IS 4923 (hollow steel sections); steel density 7,850 kg/m³; weight formula kg/m = 4 × t × (A − t) × 0.00785.