Approximately 5,082 standard 11 inches helium balloons will be required to lift an adult human having a weight of 137 pounds (62 kg).
we know that helium gas has a lifting force of 1.0715 gram per liter and a standard 11″ balloon has approximately 11.4 liters of volume. Thus, an 11″ helium balloon can lift an object of 12.2 gram (1.0715*11.4).
In order to lift a person of 62 kg (62000 gram), 5082 (62000/12.2) 11″ helium gas balloons will be required.
The number of helium balloons needs to lift a person = weight (kg) x 82.