SIP & rupee-cost averaging: investing in instalments
A SIP invests a fixed amount at regular intervals; rupee-cost averaging is the arithmetic of what that does to average cost.
General investing education — not investment advice. These explainers describe concepts in plain language; they do not assess any fund, security, or person's situation. Investing involves risk, including possible loss of principal. For guidance on personal decisions, consult a SEBI-registered investment adviser.
Not investment advice.
What a SIP is
A systematic investment plan (SIP) is a facility for investing a fixed amount into a mutual-fund scheme at a regular interval — usually monthly. It is a method of investing, not a separate product: the money goes into the same scheme it would in a lump sum, just spread over time.
The arithmetic: rupee-cost averaging
Because the instalment is a fixed rupee amount, it automatically purchases more units when the NAV is lower and fewer when it is higher. As a hypothetical illustration: ₹1,000 invested monthly at NAVs of ₹50, ₹40, and ₹50 acquires 20 + 25 + 20 = 65 units — an average cost of about ₹46.15 per unit, slightly below the simple average NAV of ₹46.67 over those months. This is a hypothetical illustration with assumed figures (authored June 2026), not a projection of any actual investment. Real returns vary and may be negative.
What it does — and does not — do
- It removes the need to decide when to invest each instalment, which spreads purchases across market conditions.
- It aligns investing with how most people earn — in monthly income.
- It does not assure a profit, and it does not protect against loss in a declining market — if the market falls and stays down, a SIP portfolio falls too. This caveat appears in mutual-fund documents because it is true.
A habit, not a verdict
Whether instalments or a lump sum produced the better historical result depends entirely on the period — neither method wins universally. The SIP is best understood as a discipline mechanism whose value is behavioural as much as arithmetic.
Related concepts: compounding, volatility.