Steel Tubes according BS 1387
Dimensions and weights of steel tubes according British Standard - BS - 1387:1985
Dimensions and weight of steel tubes according the British Standard - BS - 1387:1985 can be 
found in the table below: 
Nominal bore  Outside diameter Thickness Mass
Light Medium/ Light Medium Heavy Light Medium Heavy
Heavy
in mm mm mm mm mm mm kg/m kg/m kg/m
 1/4" 8 13.6 13.9 1.8 2.3 2.9 0.515 0.641 0.765
 1/8" 10 17.1 17.4 1.8 2.3 2.9 0.67 0.839 1.02
 1/2" 15 21.4 21.7 2 2.6 3.2 0.947 1.21 1.44
 3/4" 20 26.9 27.2 2.3 2.6 3.2 1.38 1.56 1.87
1 25 33.8 34.2 2.6 3.2 4 1.98 2.41 2.94
1 1/4 32 42.5 42.9 2.6 3.2 4 2.54 3.1 3.8
1 1/2 40 48.4 48.8 2.9 3.2 4 3.23 3.57 4.38
2 50 60.2 60.8 2.9 3.6 4.5 4.08 5.03 6.19
2 1/2 65 76 76.6 3.2 3.6 4.5 5.71 6.43 7.93
3 80 88.7 89.5 3.2 4 5 6.72 8.37 10.3
4 100 113.9 114.9 3.6 4.5 5.4 9.75 12.2 14.5
5 125   140.6   5 5.4   16.6 17.9
6 150   166.1   5 5.4   19.7 21.3
The standard is applicable to tubes of nominal size DN8 to DN150 in light, medium and heavy thickness.
The BS 1387:1985 specification for screwed and socket steel tubes and for plain end steel tubes suitable for  
 welding or for screwing to BS 21 pipe threads.