Calculation of Number of Pi and Sigma bonds in a Molecule

PI bond is formed by axial overlapping.
SIGMA bond is formed by lateral overlapping
A SIGMA bond alone can exist in a molecule, but PI bond cannot.

How to calculate number of Pi and sigma bonds in molecule.

Every single bond in a molecule is formed by sigma bond.
Every double bond in a molecule is formed by a sigma bond and a Pi bond.
On the basis of this number of sigma and Pi bonds can be calculated.

Eg: CH~^3-CH=CH-CH~^3

Number of Sigma Bonds: 3
Number of π bonds : 1