text: From the reference attached, 1 m^3 will lift 1 kg. \n\nso 100/2.2 m^3 are necessary to lift 1kg, more or less\n\nHowever, it is better to figure it out carefully.\n\nD=density of air at sea level, temperature T\nDHe=density of helium at sea level, temperature T\n\nBuoyant force of helium of volume V is equal to weight of air displaced (Archimedes), so \nB=D*V*g\nwhere g is acceleration of gravity. \nWeight of helium of volume V is DHe*V*g\n\nWeight to be lifted is W\n\nSo to balance these, \n\nB=DHe*V*g+W\nor \nD*V*g=DHe*V*g+W\n\nand V*(D-DHe)*g=W\nso V=W/[g*(D-DHe)]\n\nJust substitute for W, g, D, DHe and you have your answer.