The formula is 2number of elements in the set This set {1,2,3} has 3 elements, so the number of subsets is gotten by substituting 3 for the number of elements in the set: 2number of elements in the set = 23 = 2x2x2 = 8 So there are 8 subsets. They are 1. { } or ∅, the empty set, sometimes called the "null" set. 2.