A simple SIP formula — the 15-15-15 rule — suggests you can build a ₹1 crore corpus by investing ₹15,000 a month for 15 years at an assumed 15 percent return. It sounds neat and achievable, but how practical is it? Here’s a closer look at the maths, assumptions and risks behind the strategy.
The rule rests on three basic assumptions:
Monthly SIP: ₹15,000
Investment period: 15 years
Expected return: 15 percent annually
If these conditions hold, the final corpus works out to a little over ₹1 crore. The simplicity of the framework has made it popular among first-time investors trying to understand long-term wealth creation through mutual funds.
At a monthly SIP of ₹15,000 over 15 years, the total investment comes to about ₹27 lakh. At a 15 percent annual return, the corpus can grow to roughly ₹1.01 crore.
The key driver here is compounding. Returns generated over time begin to earn further returns, significantly boosting the final value. In this case, the gains (around ₹74 lakh) far exceed the original investment.
A 15 percent annual return is not impossible, but it is not guaranteed either. Long-term data shows that equities can deliver strong returns, but they rarely move in a straight line.
For instance, the Nifty 50 Total Return Index has delivered around 13.3 percent annually between June 1999 and December 2025. Some categories such as mid cap, small cap and flexi cap funds have delivered 15 percent or more over long periods, but these are averages, not fixed outcomes.
Returns can vary widely:
Some years may deliver over 20 percent
Others may see low or even negative returns
Even small variations in returns can significantly change the final corpus over 15 years. That is why the 15-15-15 rule should be treated as a guideline, not a promise.
The biggest risk is assuming steady returns. Equity mutual funds are market-linked, and volatility is inevitable.
Other practical factors include:
Expense ratios and charges that reduce returns
Taxes at the time of redemption
Inflation, which erodes real purchasing power
A ₹1 crore corpus 15 years from now may not have the same value as it does today.
Investor behaviour also plays a critical role. Many investors stop SIPs during market downturns or redeem investments at the wrong time, which can derail long-term plans.
The 15-15-15 rule works only if certain conditions are met:
Start early to maximise compounding
Invest consistently without breaks
Stay invested during market downturns
Avoid frequent portfolio tracking and emotional decisions
Delaying investments by even a few years can make the target harder to achieve, often requiring a higher monthly SIP to compensate.
The 15-15-15 rule is a useful way to understand the power of disciplined investing and compounding. But it is not a guaranteed path to ₹1 crore.
Investors should focus less on fixed return assumptions and more on consistency, time in the market and realistic financial planning.
Disclaimer: This article is for informational purposes only and does not constitute investment advice. Returns mentioned are indicative and based on assumptions; actual returns may vary depending on market conditions.