Recommend a read on this exact topic by @jk321
I have posted the main essence, but it is recommended to view the complete blog post.
So, the magical number for a 30 year old with annual expense of 6 lakh is 2.22 cr (assuming he continues to cover medical, leisure expense etc in this annual expense only).
For a remaining life of 70 years, we need 40 times expense & for 80 years remaining, we need around 43 times.
So, 37-40 times annual expense is enough!
However, since equity returns will be lumpy, a negative return in early years will hurt. Hence, we need to build some Margin of safety into the formula.
Hence, 50 times annual expense should be enough! (except in extreme situations)
And that’s not impossible provided we take care of P, r and n of the Compounding equation.
PS: Maybe Jatin could clarify in case of any clarifications.