The specific surface area determination of activated carbons by means of the low-temperature argon adsorption (the BET method) was compared with the measurement of the surface area based on the adsorption of I-2 from the aqueous KI solution. It is proposed to recalculate the iodine adsorption number for the BET surface area. It is shown that the SIN method can be used for a quick estimation of the structure development of porous carbonaceous materials.