How to Calculate the Retirement Corpus You Need

Retirement planning requires estimating two things: how much money you will need each month after you stop working, and how large a savings corpus will sustain those withdrawals for your full retirement period. Because inflation erodes purchasing power over time, your current monthly expenses cannot be used directly — they must be projected forward to your retirement date using an estimated annual inflation rate (typically 5–7% for India).

The 25× Annual Expense Rule

The 25× rule (based on the 4% safe withdrawal rate) states that you need a retirement corpus equal to 25 times your annual expenses at retirement. This ensures you can withdraw 4% of your corpus every year without depleting it over a 25–30 year retirement.

Required Corpus = Inflation-Adjusted Annual Expenses × 25

Worked Example

Current monthly expenses: ₹50,000. You plan to retire in 20 years. Assumed inflation: 6% per year.

If you already have ₹10 lakh saved and it grows at 10% over 20 years, it becomes ₹67 lakh — reducing the SIP requirement. Use the calculator above to input your exact figures and get a personalised retirement savings plan.