Walk into any steel dealer in Nepal and you will hear sizes thrown around — "8 sutta", "12 sutta", 16 mm, 20 mm. Each diameter has a distinct job in a building. This guide explains what every common TMT bar size is used for, and roughly what it weighs, so you can read your engineer's estimate with confidence.
How Bar Size, Weight, and Cost Relate
Steel is sold by weight, but used by length and diameter. The standard weight of a bar rises with the square of its diameter — a 16 mm bar is not twice as heavy as an 8 mm bar, it is about four times heavier. Approximate weights per metre:
- 8 mm ≈ 0.395 kg/m
- 10 mm ≈ 0.617 kg/m
- 12 mm ≈ 0.888 kg/m
- 16 mm ≈ 1.580 kg/m
- 20 mm ≈ 2.470 kg/m
- 25 mm ≈ 3.850 kg/m
- 32 mm ≈ 6.310 kg/m
These standard weights come from the formula d²/162 (kg per metre, d in mm). Consistent weight per metre is itself a quality check — a bar significantly lighter than standard has been rolled undersize.
Size-by-Size: Where Each Bar Is Used
8 mm — the workhorse of secondary reinforcement
Stirrups (the rings that wrap around column and beam bars), distribution steel in slabs, and ties. Almost every structure uses large quantities of 8 mm.
10 mm — slabs and light elements
Main reinforcement in residential slabs, lintels, and smaller elements such as sunshades and shelves.
12 mm — the residential mainstay
Beams and slabs in typical houses, staircases, and secondary members in larger buildings. For many 1–2 storey homes, 12 mm is the largest bar on site.
16 mm — columns and primary members
Column verticals and main beam bars in multi-storey houses and commercial buildings.
20 mm — heavy residential and commercial
Columns and footings of taller or heavily loaded buildings, transfer beams, and long spans.
25 mm and 32 mm — infrastructure scale
Bridge work, industrial foundations, hydropower structures, and high-rise columns. These sizes are usually specified only in engineered, large-scale projects — Bajrang Steel supplies them to hydropower and highway projects across Eastern Nepal.
Reading an Estimate: A Quick Example
A typical two-storey house order might look like: a few hundred kg of 8 mm for stirrups, similar of 10 mm for slabs, the largest share in 12 mm for beams and slabs, and 16 mm for columns. If your quotation is heavily skewed toward sizes that do not match your drawings, ask questions before paying.
Buying Tips, Whatever the Size
- Buy all sizes from the same certified manufacturer — mixing brands mixes tolerances.
- Check the brand and size embossed on the bar itself, not just the tag on the bundle.
- Verify weight: weigh a measured length and compare against the standard kg/m above.
- Store bars off the ground and covered — surface rust from site storage is normal and brushes off, but prolonged exposure pits the steel.
Final Thoughts
Bar sizes are a system, not a menu — each diameter does a specific structural job, and your engineer's design balances them. Your job as a buyer is simpler: make sure every size that arrives on site is certified, full-weight, and from a producer you trust.
Bajrang Steel Team
Written by the team at Swastik Rolling Mills Pvt. Ltd. — manufacturer of NS-191 certified Fe 500 TMT bars and structural steel in Duhabi, Biratnagar. For project-specific advice, always consult a qualified structural engineer.
