🎓 Mutual Funds & Investment
The 15x15x15 Rule in Mutual Funds — The Math That Turns ₹15,000 into ₹1 Crore
What is the famous 15x15x15 rule of mutual funds? The exact math of the power of compounding — a ₹15,000 monthly SIP at 15% returns growing to ₹1 crore in 15 years, fully explained.
Introduction
Hearing “₹1 crore” makes it sound like rich people’s arithmetic. But the math of the power of compounding says — ₹15,000 a month, given enough time, puts that sum within reach of an ordinary salaried person. The 15x15x15 rule is the well-known name for that calculation.
What Compounding Actually Is
With simple interest, you earn only on the principal. With compounding, the earnings start earning too:
- ₹100 at 10% → ₹110 at the end of the year.
- In the second year the interest is earned not on ₹100 but on ₹110 → ₹121.
- Year after year this bonus keeps growing — the earnings snowball like a snowball (Snowball).
The Exact Math of 15x15x15
The three 15s:
- ₹15,000 per month SIP
- 15% annual return (CAGR)
- 15 years uninterrupted
The result:
| Item | Amount |
|---|---|
| Your total contribution (15,000 × 12 × 15) | ₹27,00,000 |
| Estimated gains | approx. ₹74,52,000 |
| Total corpus | approx. ₹1,01,52,000 |
Notice: you contributed ₹27 lakh, but more than ₹74 lakh was earned by your money itself — that is compounding.
What It Comes To at 12%
If the return is 12% (close to Nifty’s long-term average), the same SIP over 15 years comes to about ₹75 lakh. Remember the difference — a 3% gap in rate becomes ₹25 lakh over the long term, so fund selection and fees (expense ratio) matter.
Stretch the Time and It Turns Supernatural
The same ₹15,000 SIP, if never stopped:
| Tenure | Total Contribution | Estimated Corpus (15%) |
|---|---|---|
| 15 years | ₹27 lakh | ~₹1.01 crore |
| 20 years | ₹36 lakh | ~₹2.27 crore |
| 25 years | ₹45 lakh | approx. ₹4.9 crore |
| 30 years (15x15x30) | ₹54 lakh | approx. ₹10.5 crore |
The money made in the last 5 years is no more than what the first 10 years made — the graph goes almost vertical (Vertical) at the end. Meaning: the real cost of delaying isn’t felt intuitively, only in the math.
Rules for Putting the Rule to Work
- Start early, keep going uninterrupted — stopping the SIP when the market falls is this rule’s biggest enemy.
- To increase your SIP in stages, see Step-Up SIP.
- To calculate with your own amount and tenure, use the SIP Calculator or the Step-Up SIP Calculator.
- If choosing flexi cap/mid cap for the 15% target, understand the risk: Mid Cap vs Flexi Cap.
Final Word
15x15x15 is no magic wand — the three numbers stand for regular saving, reasonable expectation, and patience. Two of the three are in your hands, the third (returns) is in the market’s. Manage what you control, and start.
❓ Frequently asked questions
What are the three 15s of the 15x15x15 rule?
A ₹15,000 monthly SIP, an expected annual return of 15% (CAGR), and continuing it uninterrupted for 15 years — when the three 15s come together, the corpus crosses roughly ₹1 crore.
Is a 15% return realistic?
Not guaranteed, but over the long history of the Sensex/Nifty the Indian stock market has delivered 12-14% average returns. A 15% target usually requires comparatively riskier funds such as flexi cap or mid cap. You can conservatively assume 12% — then the corpus in 15 years is around ₹75 lakh.
When does compounding become visible?
For the first 3-4 years you won't see any big effect — the real magic starts after the 7th-8th year, when the earnings accumulated begin to exceed your own contributions. So the hardest part of this rule is not the math, it's patience.