About the retirement calculator
Two questions sit behind every retirement plan, and most calculators only answer the first. What will I have saved by the time I stop working, and how long will that actually last me once I do? This runs both phases end to end: a lumpsum and a monthly SIP compounding until your retirement age, then withdrawals coming out of whatever that built.
The number that decides everything is the one people state casually. If you say you want fifty thousand a month in retirement, you mean fifty thousand of today's money — a life that looks like the one you have now. In thirty years at six percent inflation that same life costs about two lakh eighty-seven thousand a month. This calculator inflates your figure to your retirement date before it withdraws a single rupee, and keeps raising it every year afterwards. Planning in flat nominal rupees is the single most common way a retirement projection ends up cheerfully, dangerously wrong.
Returns are set separately for the two phases, because the money is doing a different job in each. While you are accumulating, a fall recovers and you keep buying through it. Once you are drawing an income, a fall means selling more units to raise the same rupees, so most people move toward something steadier and accept a lower return for it. Using one optimistic figure across forty years flatters the answer at exactly the point it matters most.
You can also keep contributing after retiring. Consultancy, a rental, a part-time role — anything that lets you put money in while taking money out extends the corpus considerably, and the tool shows by how much. Contributions land after each month's withdrawal, so income arriving later can never disguise a month the corpus could not cover on its own.
What this does not model: tax on withdrawals, expense ratio, exit load, and — the largest omission — sequence risk. A market fall in the first few years of retirement does far more damage than the same fall twenty years in, because you are selling units to live on while prices are low. A steady annual percentage is a convenient fiction. Treat the answer as arithmetic that tells you whether the plan is roughly right, not as a forecast.