Like I said before, the first thing you do is estimate numbers. Life spans, medical expenses etc. I will give you few rules of thumb people use to estimate lifespans if you do not have any terminal illness. Generally, the number of years until death are estimated as (100-age)/2. If you do not have any terminal illness and your age is 60 then you have 20 more years to live.
Now, you also have to account for how much you will end up spending on others based on your obligations towards your parents. Indian government will mandate that you pay no higher than

10,000 per month to your parents (
Maintenance and Welfare of Parents and Senior Citizens Act, 2007 - Wikipedia). You have to consider that aspect into your calculations. If you read the law then Indian government would even hold grandchildren accountable for their grandparents as long as grandchildren are adults.
There is a similar formula on what percent of your portfolio should be invested in stocks. Generally, people use (120-age). If your age is 30 then you should have 90% invested in stocks. The formula is American where retirement age is higher. In Indian context, you may use (100-age). This means at age 30, you should have 70% invested in stocks and rest in conservative investments like gold, cash in bank (demonotization risk in held in hand), and bonds.
There is an investment thread and also I believe a similar retirement thread where many options were discussed 3-4 years ago. Here is that thread.
Retirement Planning