Yearly compounding
The maturity is the amount times (1 + yearly rate), raised to the number of years. A 12% year turns ₹100 into ₹112. The next year, 12% is charged on ₹112, not on the original ₹100. That is the whole formula. The rate is one you type. It is not a fund’s past return, and it does not change halfway unless you run the page again.
A worked example
₹5,00,000 at 12% for 10 years grows to ₹15,52,924. The gain is ₹10,52,924. At 6% inflation the same maturity is ₹8,67,145 in today’s rupees.
As equity held for 10 years, the first ₹1,25,000 of the gain is exempt. Tax is ₹1,15,991 and cess is ₹4,640. After tax the maturity is ₹14,32,293.
The same ₹5,00,000, paid as ₹41,667 a month for 12 months and then left to grow, ends at ₹14,80,053. The lump sum is ahead because the whole amount earns a return from the first year. The SIP calculator still has a lump-sum tab. This page is the one to use for a single investment.
Tax on the gain
Equity long-term gains above ₹1,25,000 are taxed at 12.5% under Section 198. Short-term equity gains, on units held for not more than 12 months, are taxed at 20% under Section 196. Health and education cess is 4% of that tax. Surcharge is not added, because the rest of your income is unknown.
A debt fund, with the equity switch off, is taxed at the slab you pick, plus the same cess. The capital gains calculator covers indexation, house property and other assets. A monthly plan is the SIP calculator. Taking money out later is the SWP calculator. A bank deposit is the FD calculator.
This is an estimate for learning, not advice. Read the disclaimer.