SIP Calculator Explained: How Compounding Builds Wealth

A SIP (Systematic Investment Plan) is simply investing a fixed amount at regular intervals — usually monthly — into a mutual fund, instead of investing a lump sum once. The math behind why this works so well long-term is compounding, and seeing the actual numbers is usually what makes it click.

The formula behind the number

A SIP's future value isn't just monthly amount × number of months — each individual instalment keeps earning returns for the remaining time until maturity, so early instalments compound for much longer than later ones. The standard formula is FV = M × [((1 + i)ⁿ − 1) / i] × (1 + i), where M is the monthly investment, i is the monthly rate of return, and n is the number of months. The extra (1 + i) at the end accounts for each instalment being invested at the start of the month, not the end — the standard SIP convention.

Step-by-step: run the numbers

1. Open the Calculator Hub and switch to the SIP tab.
2. Enter your monthly investment amount.
3. Enter an expected annual return — for equity mutual funds, many use a long-term historical average, but returns are never guaranteed.
4. Enter your investment duration in years.
5. Read off the future value, total invested, and estimated gains.

Why starting early matters so much

Because each instalment compounds for however long is left until maturity, money invested in year one has decades to grow, while money invested in the final year barely compounds at all. This is why the same total amount invested, spread over a longer period starting earlier, almost always beats a larger amount invested over a shorter period starting later — time in the market is doing most of the work, not the size of any single instalment.

What a SIP calculator can't tell you

The expected-return figure you enter is an assumption, not a guarantee — actual mutual fund returns vary year to year and can be negative in bad years, even if the long-term average works out positive. Use the calculator to understand the shape of compounding and to compare different scenarios, not as a promise of what you'll actually receive.