2.1Masses
The masses per metre have been calculated assuming that the density of steel is 7850 kg/m^{3}.
In all cases, including compound sections, the tabulated masses are for the steel section alone and no allowance has been made for connecting material or fittings.
2.2Ratios for local buckling
The ratios of the flange outstand to thickness (c_{f} / t_{f}) and the web depth to thickness (c_{w} / t_{w}) are given for I, H and channel sections.

for I and H sections 

for channels 

for I, H and channel sections 
For circular hollow sections the ratios of the outside diameter to thickness (d / t) are given.
For square and rectangular hollow sections the ratios (c_{f} / t) and (c_{w} / t) are given where:

and 

For square hollow sections c_{f} and c_{w} are equal. Note that these relationships for c_{f} and c_{w} are applicable to both hotfinished and coldformed sections.
The dimensions c_{f} and c_{w} are not precisely defined in EN 199311 and the internal profile of the corners is not specified in either EN 102102 or EN 102192. The above expressions give conservative values of the ratio for both hotfinished and coldformed sections.
2.3Dimensions for detailing
The dimensions C, N and n have the meanings given in the figures at the heads of the tables and have been calculated according to the formulae below. The formulae for N and C make allowance for rolling tolerances, whereas the formulae for n make no such allowance.
2.3.1UB sections, UC sections and bearing piles
N 
= (b  t_{w}) /2 + 10 mm 
(rounded to the nearest 2 mm above) 
n 
= (h  d) /2 
(rounded to the nearest 2 mm above) 
C 
= t_{w} /2 + 2 mm 
(rounded to the nearest mm) 
2.3.3Parallel flange channels
N 
= (b  t_{w})+ 6 mm 
(rounded to the nearest 2 mm above) 
n 
= (h  d) /2 
(rounded to the nearest 2 mm above) 
C 
= t_{w} + 2 mm 
(rounded to the nearest mm) 