What is a SIP (Systematic Investment Plan)?
A SIP (Systematic Investment Plan) is a mode of investing in mutual funds where the investor commits a fixed amount on a fixed date every month (or week, fortnight, or quarter) via auto-debit from a bank account, buying more units when prices fall and fewer when prices rise. SIPs enforce discipline, average cost over market cycles (rupee-cost averaging), and let retail investors compound small contributions into large long-term corpora.
Detailed definition
A SIP is not a product, it is a mode of investing. The underlying product is still a mutual fund scheme regulated by SEBI under the SEBI (Mutual Funds) Regulations, 1996. You can SIP into an equity fund, a debt fund, a hybrid fund, a gold ETF, or a tax-saving ELSS scheme. The SIP layer just automates the purchase: a fixed rupee amount is debited from your bank on a chosen date each interval and converted into NAV-based units at that day's net asset value.
The economic logic is rupee-cost averaging. When the NAV is Rs 100, your Rs 5,000 buys 50 units. When the NAV falls to Rs 80, the same Rs 5,000 buys 62.5 units. Over a full market cycle the average cost per unit ends up below the simple-average NAV of the period. This works because volatility is mathematically asymmetric: a 50 percent fall requires a 100 percent gain to recover, and SIPs accumulate cheap units during the fall that benefit from the rebound.
SIPs also solve behavioural problems. The data on lump-sum investing shows most investors fail to time entry well; they buy after a rally and sell during a panic. A SIP removes the timing decision by enforcing a calendar-driven purchase regardless of sentiment. The Association of Mutual Funds in India (AMFI) reports that as of April 2025, monthly SIP inflows had crossed Rs 26,000 crore across roughly 9.4 crore live SIP accounts, the highest in the industry's history.
Formula
FV = P x [((1 + r)^n - 1) / r] x (1 + r) where: FV = future value of the SIP corpus P = fixed installment amount (e.g. Rs 5,000 per month) r = periodic rate of return (annual % / 12 for monthly SIP, as decimal) n = total number of installments (years x 12 for monthly SIP) Step-up SIP (annual growth g): FV approx = sum over each year of P_year x ((1+r)^(12) - 1)/r x (1+r) compounded forward P_year+1 = P_year x (1 + g)
- P is the per-installment amount in rupees; do not divide annual into monthly without dividing rate too.
- r is the periodic rate as a decimal. For 12 percent annual monthly SIP, r = 0.12 / 12 = 0.01.
- n is total installments, not years. A 20-year monthly SIP has n = 240.
- The trailing (1 + r) term assumes investments are at the start of each period; remove it for end-of-period.
- For irregular dates and amounts, use XIRR in Excel or the Google Sheets
XIRR()function instead of this closed form.
Worked example
Suppose Rohan starts a Rs 5,000 monthly SIP at age 30 in an Indian equity index fund and lets it run for 20 years, assuming a long-run CAGR of 12 percent (close to the Nifty 50 TRI 20-year rolling average through 2024).
- Installment P: Rs 5,000.
- Periodic rate r: 12 / 12 = 1 percent, or 0.01 in decimal.
- Total installments n: 20 x 12 = 240.
- Compounding factor: (1.01)^240 = 10.893.
- Future value: 5000 x ((10.893 - 1) / 0.01) x 1.01 = 5000 x 989.3 x 1.01 = Rs 49.96 lakh.
- Total capital invested: 5000 x 240 = Rs 12,00,000.
- Gain: Rs 37.96 lakh, a 4.16x multiple on invested capital.
SIP versus lump sum
The lump-sum-versus-SIP debate has a defensible answer: it depends on market direction during the deployment period. The math:
| Dimension | SIP | Lump sum |
|---|---|---|
| Rising market | Underperforms (later buys are at higher NAVs) | Outperforms (full corpus compounds from day one) |
| Falling / sideways market | Outperforms (averages down on dips) | Underperforms (full corpus exposed to drawdown) |
| Behavioural risk | Low (auto-debit, no decision) | High (timing risk and regret) |
| Best for | Salaried investors with monthly cash flow | Bonus, inheritance, one-time windfall |
| 20-yr rolling Nifty 50 (SBI MF study) | Wins ~25% of 20-yr windows on absolute return | Wins ~75% on absolute return but has higher worst-case drawdown |
| Hybrid (recommended) | If you have a windfall, deploy ~50% as lump sum and ~50% via a 12-month SIP/STP into the same fund. | |
Common pitfalls
- Stopping during a correction. The single biggest mistake. The whole point of a SIP is buying more units cheaply during a fall. Investors who paused SIPs in March 2020 (COVID crash) missed the cheapest 12 months in a decade.
- Choosing the wrong fund. SIP into a poorly-managed scheme with high TER is just a slow way to lose money. Check the expense ratio (under 1.5 percent for actively managed equity, under 0.5 percent for index funds) and 5-year rolling returns vs the benchmark.
- Ignoring tax. Each SIP installment in equity funds has its own 1-year holding period for LTCG eligibility. Selling units bought in the last 12 months triggers 20 percent STCG (FY 2024-25 onwards), not 12.5 percent LTCG.
- Not stepping up. A flat Rs 5,000 SIP for 20 years assumes your income never grows. A 10 percent annual step-up roughly doubles the final corpus.
- Over-diversifying. Running 8 SIPs across 8 funds with overlapping portfolios just adds tracking work. Two or three well-chosen funds (one large-cap index, one mid/small-cap active, one debt) cover most goals.
Related terms
Related calculators on 3Tej
Run your own SIP scenarios with the calculators below:
Frequently asked questions
What is a SIP in mutual funds?
A SIP, or Systematic Investment Plan, is a way to invest a fixed amount in a mutual fund scheme at regular intervals (most commonly monthly) via auto-debit. The same rupee amount buys more units when the NAV is low and fewer when it is high, smoothing out entry price over time. This is called rupee-cost averaging. SIPs are offered by every AMC under SEBI regulation and have been available in India since Franklin Templeton launched the first one in 1993.
How is SIP future value calculated?
The future value of a SIP with monthly contributions is FV = P x [((1 + r)^n - 1) / r] x (1 + r), where P is the monthly contribution, r is the monthly rate of return (annual rate divided by 12), and n is the total number of monthly installments. For Rs 5,000 per month at 12 percent annual return over 20 years, P = 5000, r = 0.01, n = 240, which gives FV approximately Rs 49.95 lakh on a total invested capital of Rs 12 lakh.
What is the difference between SIP and lump sum?
A lump sum invests the entire amount in one go; a SIP spreads it over multiple installments. Mathematically, in a steadily rising market the lump sum wins because money is in the market longer. In a volatile or sideways market, the SIP wins because rupee-cost averaging buys cheaper units during dips. The SBI Mutual Fund 2024 study of 20-year rolling periods on the Nifty 50 found lump sum delivered higher returns in roughly 75 percent of windows, but SIP delivered lower worst-case drawdowns in every window.
What is a step-up SIP?
A step-up SIP (also called top-up SIP) increases the monthly contribution by a fixed percentage or rupee amount each year, typically matching annual salary growth. A 10 percent annual step-up on a Rs 5,000 starting SIP for 20 years at 12 percent return produces roughly Rs 1.05 crore versus Rs 49.95 lakh from a flat SIP, on total invested capital of roughly Rs 34 lakh versus Rs 12 lakh. The step-up captures the compounding power of higher contributions made later in the cycle.
Is SIP safer than a lump sum?
SIP reduces the risk of timing the market badly with a single entry, but it does not protect against equity-market risk itself. If you SIP into a falling market for 5 years, your portfolio still falls. SIPs work best for long-horizon (10+ year) goals in equity funds where time in the market and rupee-cost averaging combine. For short-horizon goals (under 3 years), a debt fund or fixed deposit is usually safer than even a SIP into equity.
What is the minimum SIP amount in India?
Most AMCs allow SIPs starting at Rs 500 per month, and several now offer Rs 100 SIPs (HDFC, Nippon India, SBI). SEBI does not prescribe a minimum; the floor is set by the fund house. The smaller starting amounts are designed to bring first-time investors into the mutual fund ecosystem. The 2024 AMFI data shows the average SIP ticket size in India is approximately Rs 2,500 per month.
Sources and further reading
- SEBI, SEBI (Mutual Funds) Regulations, 1996 - the umbrella regulation governing all Indian mutual funds and SIP frameworks.
- AMFI (Association of Mutual Funds in India), Industry data and SIP statistics - monthly SIP inflows and folio counts.
- SBI Mutual Fund (2024) - SIP vs Lump Sum: 20-year Rolling Period Analysis of Nifty 50 TRI.
- Franklin Templeton India - launched the first SIP scheme in India in 1993, predating the modern AMFI framework.
- Investopedia, Dollar-Cost Averaging - the global analog of rupee-cost averaging.