A SIP invests a fixed amount in a mutual fund every month. The projection below uses 12% a year, a planning figure and not a promise. Returns vary and can be negative.
With ₹10,000 a month for 15 years, the formula gives roughly ₹50.46 lakh, of which ₹18 lakh is your own contribution. Stretch the same SIP to 25 years and it becomes about ₹1.9 crore.
The formula is FV = M × ((1 + i)N − 1) ÷ i × (1 + i), where M is the monthly amount, i is the monthly return (1% here) and N is the number of instalments (180 for 15 years). The last ten years of the 25 add more than the first fifteen, which is the whole case for starting early.
Try your own amount, period and return in the SIP calculator, which also shows a year-by-year table. This is general information, not investment advice.