What Is a SIP?
A Systematic Investment Plan (SIP) lets you invest a fixed amount at regular intervals — usually monthly — into a mutual fund, rather than investing a large lump sum at once. Each instalment buys units of the fund at that day’s price (the Net Asset Value, or NAV).
Why SIP Returns Aren’t Calculated Like a Fixed Deposit
With a lump-sum investment, your entire amount is invested for the whole period, so a simple compound interest calculation works. With a SIP, your first instalment is invested for the full duration, but your last instalment might only be invested for a month or two — each instalment has a different holding period. This is why SIP returns are calculated using a formula that accounts for the timing of each individual contribution, commonly expressed as an XIRR (Extended Internal Rate of Return) for accuracy, or approximated using the future value of a series of periodic payments.
What Is Rupee-Cost Averaging?
Because you invest a fixed amount regularly regardless of whether markets are up or down, you automatically buy more units when prices are low and fewer units when prices are high. Over time, this averages out your purchase cost — you’re not trying to time the market, and a single bad entry point matters less than it would with a one-time lump-sum investment.
What Affects Your SIP’s Final Value
Three factors matter most: the monthly amount you invest, how long you stay invested, and the fund’s actual performance (which is never guaranteed and varies with market conditions). Of these, time in the market is often the most powerful lever for a beginner, since compounding needs time to meaningfully build up — starting a smaller SIP earlier can outperform a larger SIP started later, purely because of the extra years of compounding.
A Realistic Way to Estimate Returns
Since actual market returns vary and are never guaranteed, a SIP calculator typically asks you to enter an assumed average annual return based on historical fund/category performance, then projects a possible future value — this is an illustration for planning purposes, not a promise of what you will actually earn.