Nearly 69 million people in India use Facebook daily, of which 64 million access the platform through their mobile devices. Source: Vijay Shankar, Facebook Head of Products (Facebook Lite)
Below is a city wise breakdown.
Estimated monthly active users according to adverts : 29 Nov 2015
All India – 137,000,000
Delhi/NCR – 14,000,000
Mumbai – 8,300,000
Bangalore – 9,100,000
Chennai – 11,000,000
Kolkata – 13,000,000
As of today, about 108,000,000 people use Facebook in India making it the third largest user base for Facebook after USA and Brazil. Roughly 8.9% of Indians use Facebook. As of 2011, there were about 121 million people accessing internet in India. Here is the breakdown of the usage in the top 5 cities in India.