108 is a very sacred number and there are numerous reasons why it is used, but here are just a few!

The average distance of the Moon from the Earth is 108 times the diameter of the Moon.  

There are said to be 108 earthly desires in mortals.

There are 54 letters to the Sanskrit alphabet, each one has masculine and feminine, Shiva and Shakti.  54 X 2 = 108

Pranayama.  If one is able to be so calm in meditation as to have only 108 breaths in a day, enlightenment will come.  

In Astrology there are 12 constellations, 9 arc segments called namshas or chandrakalas.  There are 12 houses and 9 planets.  9 X 12 = 108 

The river of Ganga spans 12 degrees longitude and 9 degrees of latitude, 108.

We have 108 sounds in the universe.

We have 108 elements in the universe.

There are 108 letters in the Mul Mantra.

1 = GOD | 0 = emptiness or completeness in spiritual practice | 8 = infinity or eternity

108= 9 and 9 is the number of completion.