how many cubic ft of helium does it take to lift a person?

at atmospheric pressures, using something like say... a weather balloon.. how much helium would it take to lift a human? i bet there would be an altitude cap with just barely more than the sufficient ammount to lift them enough to be 'neutrally bouyant' so they can be lifted in ideal conditions, as opposed to an ammount that will reliably lift someone to almost 23 miles up without overdoing it ( up to  almost where helium weather balloons expand too much and pop)  if possible, please provide both measurements also, does the shape of the vessil holding the helium make a difference?