What Is Rupee-Cost Averaging, With a Real Worked Example
Investing a fixed amount every month means you automatically buy more units when prices are low and fewer when prices are high — without ever trying to time it.
The mechanism
Rupee-cost averaging happens automatically whenever you invest a fixed amount at regular intervals (like a SIP), rather than a variable amount. Because the amount is fixed but the price (NAV) moves, the same ₹10,000 buys more units when the price is low and fewer units when the price is high — pulling your average cost per unit toward the middle, without you making any deliberate timing decision.
Why this specifically helps during a volatile or falling market
This is the actual mechanism behind advice to 'keep SIPs running during a downturn' — a falling NAV means each fixed monthly instalment buys more units than it would have at the higher price, lowering your average entry cost across the whole period, which then benefits fully when prices recover.
Month 1 (NAV ₹50): buys 200 units. Month 2 (NAV ₹40, a dip): buys 250 units. Month 3 (NAV ₹35, further dip): buys ~285.7 units. Month 4 (NAV ₹45, recovering): buys ~222.2 units.
Total invested: ₹40,000. Total units: ~957.9. Average cost per unit: ~₹41.75 — noticeably lower than the starting NAV of ₹50, purely because more units were bought automatically during the dip months. Stopping the SIP during months 2-3 (a common panic reaction) would have missed exactly the months doing the most good.
Common mistakes
- Stopping a SIP during a market downturn — that's precisely when rupee-cost averaging is buying the most units at the lowest cost.
- Expecting rupee-cost averaging to guarantee a profit — it lowers average entry cost, but the investment still needs to recover and grow to actually produce a gain.
- Assuming it works the same for a lumpsum — the averaging effect specifically comes from investing at intervals, not from a single one-time investment.
Frequently asked questions
What is rupee-cost averaging?
Investing a fixed amount at regular intervals, so the same amount automatically buys more units when prices are low and fewer when prices are high — lowering your average cost per unit over time without any deliberate timing decision.
Does rupee-cost averaging guarantee a profit?
No — it lowers your average entry cost, but the investment still needs to recover and grow from there to produce an actual gain. It reduces timing risk, it doesn't eliminate market risk.
The example above uses illustrative figures — the tool is real, so change any input and it recalculates instantly.
Try the SIP calculator →