As of may 2009, there are exactly 900 million hindus in the world. this makes it the third largest religion when compared to 2.1 billion christians and 1.5 billion muslims. percentage wise, 33% people practice christianity as opposed to 21% following islam and 14% following hinduism. it is interesting to note at this stage that, there are 16% of people across the globe who do not believe in religion or are commonly referred to as aethists. hope this helps!