Some assumptions for that are as below.100+ is the best guess most experts have given various constraining factors (like nuclear energy being given the rightful priority over missile use of available Uranium).
by end of 2014 it was assumed that India had 550 kg of weapons grade plutonium, 200kg of HEU, 3 metric tons of separated reactor grade plutonium. Base assumption that only 70% of the stockpile of WGP is used for weapons, rest in reserve. India does not use HEU or the reactor grade plutonium to create weapons.
100 number is an educated guess based on the above. Above all the assumptions on stockpiles were based on judgement of Indian motivation or lack thereof, to create weapons grade plutonium and or use separated reactor grade for weapons, since India is a responsible nuclear power who does not want to use nukes. Any attempt to skew public discourse to any excessive stockpiling of nuclear material by India or 900-2000 warheads etc should be avoided.
Basically we will never know, but guess it is 100-125.