National Capital Territory of Delhi is the most populous Union Territory of India and has a diverse population of many religions & communities. At the census 2011, out of 1.68 Crore population, around 1.37 crores (81.68%) have returned themselves as followers of Hindu religion, 21.58 lakhs (12.86%) as Muslims or the followers of Islam, 5.70 Lakhs (3.40%) as Sikh, 1.46 lakhs (0.87%) as Christians, 1.66 lakhs (0.99%) are Jain. In addition 0.08% Stated as no religion & 0.01% are other religions.
Source: Census 2011
also, read Population of Delhi