New Delhi, Feb. 26 -- When most Indians think about retirement planning, they start with one crucial question: How much money will I need?

Over the last couple of years, there has been growing consensus around a practical formula:

This assumes a life expectancy of 85 years and that post-tax returns and inflation remain the same throughout retirement. In simple terms: if your return on investment (RoI) equals inflation, the corpus works. If returns are lower, you need more. If returns are higher, you need less.

For example, if you're 40 years old and your annual expenses are Rs.12 lakh, you can retire now if you have Rs.5.4 crore and earn returns equal to inflation.

If returns are 1% lower than inflation, the requirement rises to Rs.6....