TMT Bar Weight Chart as per IS 1786

TMT bar unit weight chart (6 mm to 40 mm)

The cross-sectional area and kg per metre columns are copied from IS 1786:2008 Table 1. The other columns are worked out from the kg per metre figure: weight of a 12 m bar = kg/m × 12, and bars per tonne = 1,000 ÷ weight of one 12 m bar.

Nominal mass of TMT bars as per IS 1786:2008 Table 1 kg/m and area from the standard; 12 m weight and bars per tonne are nominal and derived from kg/m
Nominal size (dia)	Cross-sectional area (mm²)	Nominal mass (kg/m)	Weight of one 12 m bar (kg)	12 m bars per tonne	Metres per tonne
6 mm	28.3	0.222	2.66	375.4	4,505
8 mm	50.3	0.395	4.74	211.0	2,532
10 mm	78.6	0.617	7.40	135.1	1,621
12 mm	113.1	0.888	10.66	93.8	1,126
16 mm	201.2	1.58	18.96	52.7	633
20 mm	314.3	2.47	29.64	33.7	405
25 mm	491.1	3.85	46.20	21.6	260
28 mm	615.8	4.83	57.96	17.3	207
32 mm	804.6	6.31	75.72	13.2	158
36 mm	1,018.3	7.99	95.88	10.4	125
40 mm	1,257.2	9.86	118.32	8.5	101

Note: these are nominal weights. Actual mill weights vary within the IS 1786 tolerance given below, so weigh the load before you bill on it.

IS 1786 also lists 4 mm and 5 mm (0.099 and 0.154 kg/m), and Amendment No. 1 (November 2012) added 45 mm (12.49 kg/m) and 50 mm (15.42 kg/m). Other sizes may be supplied by mutual agreement.

How the weight is calculated

Clause 7.2.1 of IS 1786:2008 says that, for checking nominal mass, the density of steel is taken as 0.00785 kg per mm² of cross-sectional area per metre (this is steel at 7,850 kg/m³).

Mass (kg/m) = Area (mm²) × 0.00785
For a round bar of diameter d mm, area = πd²/4, so
Mass (kg/m) = πd²/4 × 0.00785 ≈ d² / 162.2

Worked example for 16 mm: 201.2 mm² × 0.00785 = 1.579 kg/m, which the standard rounds to 1.58 kg/m. A 12 m bar is 1.58 × 12 = 18.96 kg, and 1,000 ÷ 18.96 = 52.7 bars per tonne.

We checked every row by working it out again from πd²/4 × 0.00785. All sizes agree with Table 1 to within 0.2% (the largest gap is at 20 mm: 2.466 kg/m against 2.47); the small gaps come from rounding in the standard. The d²/162 shortcut many site engineers use gives almost the same numbers (for example 0.889 kg/m for 12 mm against 0.888 in the table). When a figure is going on an invoice, use the Table 1 value.

IS 1786 tolerance on nominal mass

Clause 7.2.2 says that, unless the manufacturer and purchaser agree otherwise, the tolerances on nominal mass are as in Table 2 of the standard.

Tolerances on nominal mass, IS 1786:2008 Table 2 (percent)
Nominal size	Batch	Individual sample	Individual sample, coils only
Up to and including 10 mm	±7	−8	±8
Over 10 mm up to and including 16 mm	±5	−6	±6
Over 16 mm	±3	−4	±4

No plus tolerance is specified for an individual sample. A single sample taken from a batch is not treated as an individual sample.
No batch tolerance is specified for coils.
Batch (clause 3.1): any quantity of bars/wires of the same size and grade, in coils or bundles, presented for examination and test at one time. Batch mass is worked out from test specimens of at least 0.5 m each (clause 7.2.3.2).
Individual sample (clause 7.2.3.1): a randomly chosen sample at least 0.5 m long, weighed and divided by its actual length.

What the tolerance means for one 12 m bar Nominal 12 m weight with the Table 2 batch and individual-sample limits applied (kg)
Nominal size	Nominal 12 m weight	Batch tolerance	Batch range (kg)	Individual sample, lowest (kg)
6 mm	2.66	±7%	2.48 – 2.85	2.45
8 mm	4.74	±7%	4.41 – 5.07	4.36
10 mm	7.40	±7%	6.89 – 7.92	6.81
12 mm	10.66	±5%	10.12 – 11.19	10.02
16 mm	18.96	±5%	18.01 – 19.91	17.82
20 mm	29.64	±3%	28.75 – 30.53	28.45
25 mm	46.20	±3%	44.81 – 47.59	44.35
28 mm	57.96	±3%	56.22 – 59.70	55.64
32 mm	75.72	±3%	73.45 – 77.99	72.69
36 mm	95.88	±3%	93.00 – 98.76	92.04
40 mm	118.32	±3%	114.77 – 121.87	113.59

Table 2 applies to the mass per metre of a batch or sample, not to a single bar on a scale. The kg ranges above only show what those percentages come to at 12 m. Clause 7.2.2 also lets manufacturer and purchaser agree different tolerances.

Quick TMT weight calculator

Pick a size, enter the bar length and number of bars. The calculator uses the Table 1 kg/m value and shows the batch tolerance range for that size.

Bar size

Length of each bar (m)

Number of bars

Enter a length and a whole number of bars to see the weight.

TMT bar weight — FAQs

What is the weight of a 12 mm TMT bar per metre?

IS 1786 Table 1 gives 0.888 kg per metre for a 12 mm bar. A 12 m length therefore weighs 10.656 kg nominal, about 10.66 kg.

How is TMT bar weight calculated?

IS 1786 clause 7.2.1 takes the density of steel as 0.00785 kg per mm² of cross-sectional area per metre. For a round bar of diameter d mm, the area is πd²/4, so the mass per metre works out to about d²/162.2 kg. The common shortcut d²/162 gives nearly the same figure.

How many 12 m TMT bars make one tonne?

Divide 1,000 kg by the weight of one 12 m bar. On nominal weights that is about 93.8 bars of 12 mm, 52.7 bars of 16 mm and 33.7 bars of 20 mm. Real bars weigh a little more or less within the IS 1786 tolerance, so the count in an actual tonne will differ.

What mass tolerance does IS 1786 allow on TMT bars?

Table 2 of IS 1786:2008 allows ±7% on a batch for sizes up to and including 10 mm, ±5% for over 10 mm up to and including 16 mm, and ±3% for sizes over 16 mm. For an individual sample the limits are −8%, −6% and −4% respectively, with no plus tolerance specified. For coils only, the individual-sample limits are ±8%, ±6% and ±4%.

Why does the weighed load differ from the chart weight?

The chart gives nominal mass. Bars made to IS 1786 may vary in mass within its tolerance, so a real bundle can weigh somewhat more or less than bar count times chart weight. So weigh the load and bill on the actual weight, not on bar count times chart weight.

Source

IS 1786:2008, High Strength Deformed Steel Bars and Wires for Concrete Reinforcement — Specification (Fourth Revision), Bureau of Indian Standards: clause 6.1, Table 1, clause 7.2 and Table 2. We read Amendments No. 1 (2012), 2 (2013), 3 (2017) and 4 (2019). Only Amendment 1 touches these tables, and it just adds the 45 mm and 50 mm rows to Table 1. Last checked September 2026. For a contract or a dispute, go by the current BIS text.

Chart weight on the order, actual weight on the bill

SteelERP records the ordered weight and the actual loaded weight for each item and bills on the actual, so the difference between chart weight and loaded weight is on record for each item. You can try it on sample data in the live sandbox.

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