Number of leaf nodes in full binary tree

You start with 1 leaf node and each branching step creates 2 new leaf nodes, and one leaf node turns into an internal node (for a net of +1 leaf in the tree). So the tree has 2b+1 nodes, b internal nodes, and b+1 leaves, where b is the number of branchings.

n = 2b+1

b = (n-1)/2

The number of leaf nodes in a full binary tree with n nodes is equal to (n+1)/2.

Refrence to the above formula.