text: how much helium is necessary to lift 100lbs at sea level?   from the reference attached, 1 m^3 will lift 1 kg.   so 100/2.2 m^3 are necessary to lift 1kg, more or less  however, it is better to figure it out carefully.  d=density of air at sea level, temperature t dhe=density of helium at sea level, temperature t  buoyant force of helium of volume v is equal to weight of air displaced (archimedes), so  b=d*v*g where g is acceleration of gravity.  weight of helium of volume v is dhe*v*g  weight to be lifted is w  so to balance these,   b=dhe*v*g+w or  d*v*g=dhe*v*g+w  and v*(d-dhe)*g=w so v=w/[g*(d-dhe)]  just substitute for w, g, d, dhe and you have your answer.