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TMT bar / round bar
kg/m = π/4 × D² × 0.00785 (D in mm). IS 1786 takes steel as 0.00785 kg per mm² of cross-section per metre. The shop-floor shortcut D² ÷ 162 is about 0.12% heavier.Standard: IS 1786:2008 (TMT / high strength deformed bars); plain round bars follow the same per-metre values in IS 1732:1989.
Actual mill weights vary within IS 1786's mass tolerance, so bill the weighed load, not only this figure.
Plate / sheet
kg = L (m) × W (m) × T (mm) × 7.85, which is the same as 7.85 kg per m² for every mm of thickness.Standard: IS 1730:1989 (plates, sheets, strips and flats); its mass tables are “based on density of steel = 7.85 g/cm³”.
Actual mill weights vary within the rolling and mass tolerances of IS 1852, which IS 1730 refers to.
MS / ERW round pipe
kg/m = (OD − t) × t × 0.02466 (mm). The constant is π × 7.85 ÷ 1000. It is plain geometry, so it works for any round steel tube once you know the OD and wall.Standard: checked against the plain-end masses in IS 1239 (Part 1):2004, Tables 3 to 5. Enter OD, not nominal bore: 50 NB is about 60 mm OD, not 50.
Actual weights vary within IS 1239's mass tolerance: +10/−8% on a single light tube and ±10% on medium or heavy; per 10-tonne load, +7.5/−5% light and ±7.5% medium or heavy. These figures are from the 2004 text; check the current BIS amendments.
Square / rectangular hollow section
Area (mm²) = 2t(D + B − 2t) − 3(4 − π)t², then kg/m = Area × 0.00785. This takes the outside corner radius as 2t and the inside radius as t. On that basis it matches every IS 4923:1997 Table 1 and Table 2 weight we checked, to the second decimal.Standard: IS 4923 (hollow steel sections for structural use). The current edition is IS 4923:2017, so check the mill catalogue for its exact figure.
Actual mill weights vary within IS 4923's weight tolerance, and corner radii differ slightly from mill to mill.
Square bar
kg/m = a² × 0.00785 (side a in mm).Standard: IS 1732:1989 (steel bars, round and square), which gives ISSQ 20 as 3.14 kg/m.
Actual mill weights vary within the rolling tolerances of IS 1852, which IS 1732 refers to.
Flat bar
kg/m = W × T × 0.00785 (mm).Standard: IS 1730:1989, which gives a 50 × 6 mm flat as 2.36 kg/m and 50 × 10 mm as 3.93 kg/m.
Actual mill weights vary within the rolling and mass tolerances of IS 1852, which IS 1730 refers to.
Checked against the standards' own tables
The right-hand column is worked out live by the same code that runs the calculator. The standards round their printed weights (IS 1786, IS 1730 and IS 1732 to three significant figures, IS 4923 to two decimals), so the last digit here may differ slightly.
| Section | Standard | Standard's table (kg/m) | This calculator (kg/m) |
|---|---|---|---|
| TMT bar 12 mm | IS 1786:2008, Table 1 | 0.888 | 0.888 |
| TMT bar 40 mm | IS 1786:2008, Table 1 | 9.86 | 9.865 |
| Round bar 20 mm (ISRO 20) | IS 1732:1989 | 2.47 | 2.466 |
| Square bar 20 mm (ISSQ 20) | IS 1732:1989 | 3.14 | 3.140 |
| Flat 50 × 6 mm | IS 1730:1989 | 2.36 | 2.355 |
| Plate 10 mm, 1000 mm wide (per metre length) | IS 1730:1989 | 78.5 | 78.500 |
| Pipe 25 NB medium, 33.7 OD × 3.2 wall | IS 1239 (Part 1):2004, Table 4 | 2.41 | 2.407 |
| Pipe 50 NB medium, 60.3 OD × 3.6 wall | IS 1239 (Part 1):2004, Table 4 | 5.03 | 5.034 |
| SHS 40 × 40 × 2.6 | IS 4923:1997, Table 1 | 2.92 | 2.917 |
| RHS 122 × 61 × 5.4 | IS 4923:1997, Table 2 | 14.01 | 14.010 |
How far can real weights move?
A calculated weight is a nominal weight. Mills roll within a tolerance, so the weighbridge figure for a real consignment will differ from it. The mass tolerances in the standards we used:
- TMT bars, IS 1786:2008: batch ±7% up to 10 mm, ±5% over 10 mm up to 16 mm, ±3% over 16 mm. An individual sample may be up to −8%, −6% or −4% in the same bands.
- Pipes, IS 1239 (Part 1):2004: single tube +10/−8% light and ±10% medium or heavy; per 10-tonne load, +7.5/−5% light and ±7.5% medium or heavy. These figures are from the 2004 text; BIS has issued later amendments, so check the current edition before relying on them.
- Plates, sheets, flats and bars: IS 1730 and IS 1732 refer rolling and mass tolerances to IS 1852:1985.
- Hollow sections: IS 4923 sets weight tolerances for individual lengths and for lots. Use the current edition, IS 4923:2017.
Steel weight calculation: FAQs
Why doesn't D²/162 match the IS 1786 table exactly?
D² ÷ 162 is a rounded version of π/4 × 0.00785 (0.0061654), so it reads about 0.12 percent high. For a 40 mm bar it gives 9.877 kg/m against 9.86 kg/m in IS 1786. This calculator uses the exact cross-sectional area multiplied by 0.00785 kg per mm² per metre, the basis IS 1786 states.
Why is my SHS or RHS weight lower than the simple formula?
Hollow sections have rounded corners. IS 4923 weights take the corner radii into account; the sharp-corner formula 2(D + B − 2t) × t × 0.00785 does not, and on the IS 4923 sizes we checked it reads roughly 3 to 8 percent heavy. For 40 × 40 × 2.6 it gives 3.05 kg/m against 2.92 kg/m in the standard.
How far can an actual TMT bundle weight differ from the calculated weight?
IS 1786 allows a batch to vary by ±7 percent for bars up to 10 mm, ±5 percent over 10 mm up to 16 mm, and ±3 percent over 16 mm. An individual sample may be up to 8, 6 or 4 percent under nominal in the same size bands. That is why billing should follow the weighed load, not only the calculated weight.
Does galvanising change the IS 1239 pipe weight?
IS 1239 (Part 1): 2004 says the thickness and mass in its Tables 3, 4 and 5 apply to both black and galvanized tubes, so this calculator uses the same figure for both.
What density does this calculator use?
7.85 g/cm³ (7,850 kg/m³) for carbon and mild steel. The IS 1730 tables are based on it, IS 4923 expresses it as 0.785 kg per cm² of section per metre run, and IS 1786 as 0.00785 kg per mm² per metre. Stainless steel and other alloys are not covered here.
Sources
- IS 1786:2008, High strength deformed steel bars and wires for concrete reinforcement
- IS 1732:1989, Steel bars, round and square, for structural and general engineering purposes: dimensions
- IS 1730:1989, Steel plates, sheets, strips and flats for structural and general engineering purposes: dimensions
- IS 1239 (Part 1):2004, Steel tubes, tubulars and other wrought steel fittings, Part 1: Steel tubes
- IS 4923:1997, Hollow steel sections for structural use and the BIS product manual for IS 4923:2017
From calculated weight to billed weight
In SteelERP, each order line keeps both the ordered weight and the actual loaded weight, and the bill is raised on the actual weight. Deliveries can be split into sub-orders by kg, metre or piece, and each sub-order has its own loading, challan and delivery status.
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