As previous answers have made clear, BITS Pilani is now listed in the QS World University Rankings. International rankings are an iterative process, each year taking a fresh look at contending institutions that deserve to be included, and included institutions that ought to be displaced. For the most part, universities from India struggle in international rankings relative to their domestic reputation… this is usually because they are extremely teaching focused and thus their research is either lesser in volume, or in international recognition and influence, or both.
In recent years, leading private institutions in India have set about changing this and thus more have qualified for inclusion, and more may do so in future.
EDIT 12/02/2019
17.5k views and 99 upvotes later and I thought there might be some interest in a little additional information on the perfromance of BITS Pilani in the rankings and how it fares amongst the Indian cohort.
It remains the reality that as one of the top 1000 universities in the world, BITS Pilani can count itself with a reasonable degree of confidence to be amongst the top 5% of universities in the world. When I first visited an Indian university in 1999, the idea of some of the ascendant private institutions being amongst India’s top 30 would have seemed unthinkable, much less amongst the world’s top 5%.