Retirement planning starts with understanding your lifestyle needs. Estimate your monthly expenses in today's value and project them forward with inflation. Most experts recommend targeting a corpus that is 25-30 times your annual expenses at retirement. Factor in healthcare costs, which typically rise faster than general inflation.

Your required corpus depends on three key factors: how much you need annually at retirement, how long your retirement will last (life expectancy - retirement age), and the expected return on your corpus during retirement. A larger corpus is needed if you retire early, live longer, or expect lower investment returns during retirement.

The 4% withdrawal rule is a popular guideline - withdraw 4% of your corpus in the first year and adjust for inflation each year. However, you may need a more conservative approach if you retire early or have a smaller corpus. A systematic withdrawal plan (SWP) from mutual funds can provide regular monthly income while keeping your corpus invested.

Time is your biggest advantage in retirement planning. Starting at 25 instead of 35 can reduce your monthly SIP requirement by 50-60% for the same retirement corpus. The power of compounding means early investments do most of the heavy lifting. Even small amounts invested consistently in your 20s can grow into substantial retirement savings.