What Is a SIP (and How Its Returns Work)
Understand what a SIP is, how rupee-cost averaging and compounding grow your investment, how SIP returns are calculated, and how a SIP compares to a lumpsum.
By the ToolsHub team · Updated August 21, 2026
A SIP (Systematic Investment Plan) invests a fixed amount into a mutual fund every month. Instead of trying to time the market, you invest steadily — which spreads your entry price and lets compounding do the heavy lifting over years.
Why a SIP works
- Rupee-cost averaging — you buy more units when prices are low and fewer when high, smoothing out your average cost.
- Compounding — early instalments have the most time to grow, so the corpus ends up far larger than the sum of your deposits.
- Discipline — a fixed monthly amount is easier to sustain than large, occasional investments.
How the returns are calculated
The future value uses FV = P × (((1 + i)n − 1) ÷ i) × (1 + i), where P is the monthly amount, i the monthly return and n the number of months. Invest ₹10,000 a month for 10 years at an assumed 12% and you put in ₹12,00,000 but end up with roughly ₹23.2 lakh — the gap is returns. See it for your own numbers in the SIP Calculator.
Step-up SIPs and lumpsums
Raising your SIP a little each year as your income grows compounds into a much bigger corpus — the Step-up SIP Calculator shows the difference. And if you have a one-time amount to invest rather than a monthly one, compare it with the Lumpsum Calculator.
Frequently asked questions
- What is a SIP?
- A Systematic Investment Plan invests a fixed amount into a mutual fund every month. It spreads your entry price over time and lets each instalment compound, which is why it suits long-term goals.
- How are SIP returns calculated?
- Using the future value of a monthly investment: FV = P × (((1 + i)^n − 1) ÷ i) × (1 + i), where P is the monthly amount, i the monthly return and n the number of months. The SIP Calculator computes it for you.
- SIP or lumpsum — which is better?
- A SIP averages your entry price and suits monthly saving; a lumpsum invests a large amount at once and can do better in a steadily rising market. Compare both with the Lumpsum Calculator.
- Are SIP returns guaranteed?
- No. Mutual funds are market-linked, so returns vary year to year. Calculators use a constant assumed rate for planning, not a promise.