Usually four sheets of leaf gelatin are equal to one enveloped of granulated gelatin. Gelatin is derived from pigskin, and is used to set liquids or stabilize, such as in Stabilized Whipped Cream Recipe . Either must be rehydrated, heated, melted and dispersed, before the liquid will become jelled when cooled. There is a lot of confusion from trying to substitute granulated for leaf gelatin. Granulated gelatin needs to be rehydrated in a cool liquid before being dissolved over hot water.
Gelatins setting power has to do with the density of the liquid being set.
One envelop of granulated gelatin will set about 2 cups of water, but with mousses and creams, the same amount will set approximately 4 cups.