MS Round, Square and Flat Bar Weight Chart (kg per Metre)

Short answer

Round bar: kg per metre = diameter² × 0.006165, with the diameter in mm. Square bar: side² × 0.00785. Flat bar: width × thickness × 0.00785. Example: a 20 mm round bar weighs 2.466 kg/m, so a 6 m length is 14.80 kg, and a 50 × 10 mm flat weighs 3.925 kg/m.

The formulas

Steel weighs 7850 kg per cubic metre. For a bar with a constant cross section, the weight of one metre is the area in square metres times 7850. With sizes in millimetres this reduces to short constants:

Round bar: kg/m = d² × 0.006165
Square bar: kg/m = a² × 0.00785
Flat bar: kg/m = width × thickness × 0.00785

The round bar constant is 7850 × π / 4 ÷ 10⁶ = 0.006165. You will also see it written as d² / 162, which is the same thing rounded.

Round bar chart

Sizes from 6 mm to 50 mm. The last column tells you how many metres of that bar make a tonne, which is handy for converting a rate per tonne to a rate per metre.

Round bar, theoretical weight
Diameter	kg per metre	kg per 6 m	kg per 12 m	Metres per tonne
6 mm	0.222	1.33	2.66	4,505
8 mm	0.395	2.37	4.74	2,534
10 mm	0.617	3.70	7.40	1,622
12 mm	0.888	5.33	10.65	1,126
14 mm	1.208	7.25	14.50	828
16 mm	1.578	9.47	18.94	634
18 mm	1.998	11.99	23.97	501
20 mm	2.466	14.80	29.59	405
22 mm	2.984	17.90	35.81	335
25 mm	3.853	23.12	46.24	260
28 mm	4.834	29.00	58.00	207
32 mm	6.313	37.88	75.76	158
36 mm	7.990	47.94	95.88	125
40 mm	9.865	59.19	118.38	101
45 mm	12.485	74.91	149.82	80
50 mm	15.413	92.48	184.96	65

Square bar chart

Square bar, theoretical weight
Side	kg per metre	kg per 6 m	Metres per tonne
6 mm	0.283	1.70	3,539
8 mm	0.502	3.01	1,990
10 mm	0.785	4.71	1,274
12 mm	1.130	6.78	885
14 mm	1.539	9.23	650
16 mm	2.010	12.06	498
18 mm	2.543	15.26	393
20 mm	3.140	18.84	318
22 mm	3.799	22.80	263
25 mm	4.906	29.44	204
28 mm	6.154	36.93	162
32 mm	8.038	48.23	124
36 mm	10.174	61.04	98
40 mm	12.560	75.36	80
45 mm	15.896	95.38	63
50 mm	19.625	117.75	51

Flat bar chart

Common flat sizes. Any other size follows the same formula, so a flat that is not listed here is one multiplication away.

Flat bar, theoretical weight
Size	kg per metre	kg per 6 m	Metres per tonne
20 × 3 mm	0.471	2.83	2,123
25 × 3 mm	0.589	3.53	1,699
25 × 5 mm	0.981	5.89	1,019
32 × 5 mm	1.256	7.54	796
40 × 5 mm	1.570	9.42	637
40 × 6 mm	1.884	11.30	531
50 × 5 mm	1.962	11.77	510
50 × 6 mm	2.355	14.13	425
50 × 8 mm	3.140	18.84	318
50 × 10 mm	3.925	23.55	255
65 × 6 mm	3.061	18.37	327
65 × 10 mm	5.102	30.61	196
75 × 6 mm	3.532	21.20	283
75 × 10 mm	5.887	35.32	170
100 × 6 mm	4.710	28.26	212
100 × 10 mm	7.850	47.10	127
100 × 12 mm	9.420	56.52	106
150 × 10 mm	11.775	70.65	85
150 × 12 mm	14.130	84.78	71

Steel Table India Inspect panel for a custom flat 50 by 100 mm showing unit mass 39.25 kg per metre and unit cost 3,140 rupees per metre — A custom flat of 50 × 100 mm in Steel Table India shows 39.25 kg/m, the same as 50 × 100 × 0.00785.

Using the chart for a price

Take the kg per metre from the chart, multiply by the length and the number of pieces, then by the rate per kg. For example, 20 pieces of 16 mm round bar, each 6 m long, at an example rate of ₹70 per kg:

1.578 kg/m × 6 m × 20 = 189.4 kg × ₹70 = ₹13,255

If the rate is quoted per tonne, divide it by 1000 first. ₹70,000 per tonne is ₹70 per kg. For the full method, including what an estimate leaves out, read the guide to steel weight and cost. For rebar in particular there is a shorter rebar chart, and for plates see the plate weight chart.

Checking a size that is not listed

Use the formula above, or open Steel Table India, choose Flats or Round and Square Bar, and type your own size. The app recalculates mass, unit cost, area and section properties from the geometry at 7850 kg/m³, at your own rate per kg. Remember that these are theoretical weights. Bars as delivered can differ a little from the chart because of rolling tolerance.

Questions people ask

How do I calculate the weight of a round bar?

Square the diameter in mm and multiply by 0.006165 to get kg per metre. A 20 mm bar gives 20 × 20 × 0.006165 = 2.466 kg/m.

How much does a 12 mm MS round bar weigh per metre?

About 0.888 kg per metre, so a 6 m length weighs about 5.33 kg and a 12 m length about 10.65 kg.

What is the formula for the weight of a flat bar?

Multiply width in mm by thickness in mm by 0.00785 to get kg per metre. A 50 × 10 mm flat gives 3.925 kg/m.

How many metres of 16 mm bar make a tonne?

About 634 metres, since a metre weighs 1.578 kg and 1000 ÷ 1.578 is about 634.

Are these weights exact?

They are theoretical weights at 7850 kg per cubic metre. Delivered bars differ slightly because of rolling tolerance, so the supplier table and weighbridge figure govern an order.

Keep reading

Any bar size, in seconds

Steel Table India calculates mass and cost for flats and round bars of your own size. Free on Google Play.

For reference, not for sign-off. The weights here are theoretical values worked at 7850 kg/m³. Rolled and drawn products have tolerances, so delivered weight can differ slightly, and supplier tables govern an order. Rates are examples only. Check critical values against the relevant Bureau of Indian Standards publication and your supplier.