Rupee Cost Averaging Explained With a Worked Example
Rupee Cost Averaging (RCA) is the mechanism that makes SIPs work the way they're marketed to work — but most investors have only a fuzzy sense of the actual arithmetic behind it. Seeing it worked through numerically makes the concept far more concrete.
The Core Principle
When you invest a fixed rupee amount at regular intervals, you automatically buy more units when the price (NAV) is low, and fewer units when the price is high — because the number of units you receive is simply your fixed investment amount divided by that period's NAV. Over time, this naturally lowers your average cost per unit compared to what you'd have paid investing the same total amount in a single lumpsum at an arbitrary, unpredictable price point.
A Worked Example
Suppose an investor commits ₹10,000 per month for 6 months, and the fund's NAV moves as follows:
| Month | NAV (₹) | Units Purchased (₹10,000 ÷ NAV) |
| 1 | 100 | 100.00 | | 2 | 90 | 111.11 | | 3 | 80 | 125.00 | | 4 | 85 | 117.65 | | 5 | 95 | 105.26 | | 6 | 110 | 90.91 |
Total invested: ₹60,000 Total units accumulated: 649.93 Average cost per unit: ₹60,000 ÷ 649.93 = ₹92.32
Notice what happened: the simple average of the six NAVs is ₹93.33 [(100+90+80+85+95+110)/6], but the investor's actual average cost per unit came out slightly lower, at ₹92.32. This is the mechanical effect of Rupee Cost Averaging — because more units were bought during the lower-NAV months (months 2, 3, 4), those cheaper purchases carry more weight in the final average cost than the simple average of NAVs would suggest.
Why This Matters More During Volatility
RCA's benefit is most visible in a market that moves down and then recovers, as in this example — the investor who kept investing through the dip picked up meaningfully more units at the lower prices, and when NAV recovered to ₹110 in month 6, the entire accumulated position (all 649.93 units) benefits from that recovery, not just the units bought at the top.
What RCA Doesn't Do
It's worth being precise about the limits of this mechanism:
- RCA doesn't guarantee profit — if a fund's NAV simply declines and never recovers, RCA only means you lose less badly than a lumpsum investor would have, not that you avoid loss altogether.
- RCA works against you in a steadily rising market — if NAV simply climbs every month without a dip, each subsequent instalment buys fewer units at a higher price, and a lumpsum invested at month 1's lower NAV would have outperformed the SIP.
- The benefit fades over very long horizons — once a SIP has been running for many years, the earliest instalments dominate the accumulated corpus, and the averaging effect of any single volatile stretch matters proportionately less to the overall outcome.
Why This Matters
Rupee Cost Averaging is a real, mechanically verifiable effect — not just a marketing phrase — but it's a volatility-management tool, not a return-guarantee mechanism. Understanding the actual arithmetic, rather than the simplified pitch, is what allows an investor to correctly judge when this benefit is likely to matter and when it isn't.
How Anuj Desai & Associates Can Help
We help AMCs and distributors ensure that investor-facing explanations of Rupee Cost Averaging — a frequently used SIP-marketing concept — are presented accurately and don't cross into the kind of return-guarantee-adjacent language that draws SEBI scrutiny under advertising code norms. If your SIP marketing material or investor education content needs a compliance review, we can help.
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