Steel Weight Table: kg/m for Round Bar, Tube, Flat Bar and Pipe

Weight per metre of steel round bar 6-100 mm, square hollow sections, flat bar and pipe - with the formula kg/m = 0.00785 x area in mm2 and worked examples.

The steel weight formula: kg/m = 0.00785 x mm2

Every weight-per-metre number in this table comes from one formula: kg/m = cross-section area in mm2 x 0.00785. The constant is steel's density (7,850 kg/m3) divided by one million. A 20 mm round bar has an area of 314 mm2, so it weighs 314 x 0.00785 = 2.47 kg/m. Remember 0.00785 and you can verify any steel weight table in seconds - or use the Metal weight calculator to compute any size directly.

Round bar weight table (solid steel)

Solid round bar is the simplest case: area = pi/4 x d2.

Diameter (mm)	Area (mm2)	kg/m
6	28	0.22
8	50	0.39
10	79	0.62
12	113	0.89
16	201	1.58
20	314	2.47
25	491	3.85
30	707	5.55
40	1,257	9.86
50	1,963	15.41
60	2,827	22.20
80	5,027	39.46
100	7,854	61.65

Rebar follows the same table - a 12 mm rebar weighs 0.89 kg/m, so a 12 m bar is 10.7 kg.

Square tube (SHS) weight table

Square hollow sections subtract the inner void: area = a2 - (a - 2t)2.

Section a x a x t (mm)	Area (mm2)	kg/m
20 x 20 x 2	144	1.13
25 x 25 x 2	184	1.44
30 x 30 x 2.5	275	2.16
40 x 40 x 2	304	2.39
40 x 40 x 3	444	3.49
50 x 50 x 3	564	4.43
60 x 60 x 3	684	5.37
60 x 60 x 4	896	7.03
80 x 80 x 4	1,216	9.55
100 x 100 x 4	1,536	12.06
100 x 100 x 6	2,256	17.71

Wall thickness matters more than most people guess: doubling it from 2 mm to 4 mm on a 40 mm tube nearly doubles the weight.

Flat bar weight table

Flat bar is width x thickness x 0.00785.

Width x thickness (mm)	Area (mm2)	kg/m
20 x 3	60	0.47
25 x 5	125	0.98
30 x 5	150	1.18
40 x 5	200	1.57
50 x 5	250	1.96
50 x 6	300	2.36
60 x 6	360	2.83
80 x 6	480	3.77
80 x 8	640	5.02
100 x 8	800	6.28
100 x 10	1,000	7.85

A handy check: 100 x 10 flat bar weighs exactly 7.85 kg/m because the area is 1,000 mm2 - one kg per 127 metres of memory aid.

Pipe weight table (medium series)

Pipe removes the bore: area = pi/4 x (OD2 - ID2).

Nominal size	OD x wall (mm)	kg/m
DN25 (1 in)	33.7 x 2.6	2.00
DN32 (1.25 in)	42.4 x 2.6	2.55
DN40 (1.5 in)	48.3 x 2.6	2.93
DN50 (2 in)	60.3 x 2.9	4.10
DN65 (2.5 in)	76.1 x 3.2	5.75
DN80 (3 in)	88.9 x 3.2	6.76
DN100 (4 in)	114.3 x 3.6	9.83
DN125 (5 in)	139.7 x 4.0	13.39
DN150 (6 in)	168.3 x 4.5	18.18

Compare a 50 mm round bar (15.41 kg/m) with a DN50 pipe (4.10 kg/m): the hollow section gives up strength per weight far more slowly than solid stock.

From kg/m to project weight and cost

Multiply the table value by total length: a workshop frame of 24 m of 40 x 40 x 2 tube weighs 24 x 2.39 = 57.4 kg. Other metals scale by their density ratio - the same frame in aluminium weighs 57.4 x 0.344 = 19.7 kg, in brass 62.2 kg. The Metal weight calculator does this arithmetic for any profile, material and quantity, and the Metal Weight Formula: Steel, Aluminum, Stainless by Profile explains the density ratios behind it.

Metal weight calculator Open the linear cutting calculator