SIP vs Lumpsum: How Returns Are Calculated and Which to Choose
How SIP returns are calculated, rupee-cost averaging, step-up SIPs and lumpsum investing compared, with worked numbers for Rs 10,000 a month at 12%.
A Systematic Investment Plan (SIP) invests a fixed amount in a mutual fund every month. A lumpsum investment puts the whole amount in at once. Both can build wealth; the right choice depends mainly on whether you have the money now or earn it month by month, and on how comfortable you are with timing risk. This guide explains how the numbers work so you can make that choice sensibly.
Run your own numbers: the free SIP Calculator, Lumpsum Calculator and Step-up SIP Calculator show invested amount, estimated returns and a year-by-year chart.
How SIP returns are calculated
Most SIP calculators use the future value of a series of monthly payments made at the start of each month:
FV = P × [((1 + i)n − 1) ÷ i] × (1 + i)
- P = monthly SIP amount
- i = expected annual return ÷ 12 ÷ 100
- n = number of months
Worked example: ₹10,000 a month at 12% for 10 years
- P = ₹10,000, i = 12 ÷ 12 ÷ 100 = 0.01, n = 120
- (1.01)120 ≈ 3.3004
- FV = 10,000 × (2.3004 ÷ 0.01) × 1.01 ≈ ₹23.2 lakh
You invest ₹12 lakh and the estimated value is about ₹23.23 lakh, so the estimated gain is about ₹11.2 lakh. Remember that 12% is an assumption. Equity fund returns vary widely from year to year, and nothing is guaranteed.
For actual SIPs, the correct measure of return is XIRR, which accounts for each instalment's date. Point-to-point growth of a single amount is measured by CAGR.
How lumpsum returns are calculated
A lumpsum grows by simple compounding: FV = P × (1 + r)t. ₹12 lakh invested at once at 12% a year for 10 years becomes about ₹37.3 lakh.
That looks much better than the SIP, but it is not a fair comparison. In the lumpsum case the whole ₹12 lakh was invested from day one, whereas the SIP invested it gradually over ten years. The real question is: if you already have the money, should you invest it all now or spread it out?
Rupee-cost averaging
Because a SIP invests the same amount each month, it buys more units when prices are low and fewer when they are high. Suppose you invest ₹1,000 a month for three months as the NAV moves from ₹10 to ₹8 to ₹12:
| Month | NAV | Units bought |
|---|---|---|
| 1 | ₹10 | 100.00 |
| 2 | ₹8 | 125.00 |
| 3 | ₹12 | 83.33 |
| Total | Average NAV ₹10 | 308.33 units for ₹3,000 |
Your average cost is ₹3,000 ÷ 308.33 ≈ ₹9.73 per unit, below the simple average NAV of ₹10. Rupee-cost averaging does not guarantee a profit, but it removes the need to time the market and smooths the effect of volatility.
Step-up SIP: the most underrated habit
A step-up (or top-up) SIP increases your monthly amount every year, usually in line with salary increments. Starting at ₹10,000 a month and increasing it by 10% every year, at the same assumed 12% return for 10 years:
| Plan | Total invested | Estimated value after 10 years |
|---|---|---|
| Regular SIP ₹10,000/month | ₹12.0 lakh | ≈ ₹23.2 lakh |
| Step-up SIP, +10% a year | ≈ ₹19.1 lakh | ≈ ₹33.7 lakh |
Try different step-up rates in the Step-up SIP Calculator.
SIP vs lumpsum: side by side
| Point | SIP | Lumpsum |
|---|---|---|
| Best for | Monthly income, building a habit | Bonus, maturity proceeds, inheritance, sale of an asset |
| Timing risk | Low; spread across market levels | High; entry level matters |
| Return in a steadily rising market | Usually lower than lumpsum | Usually higher |
| Return in a falling or volatile market | Often better, thanks to averaging | Can be painful in the short term |
| Discipline | Automatic via bank mandate | One decision |
| Minimum amount | Often ₹100–₹500 a month | Often ₹1,000–₹5,000 |
Working backwards from a goal
Instead of asking what a SIP will grow to, you can ask how much you need to invest each month to reach a target. At an assumed 12% annual return, the monthly SIP needed to build ₹1 crore is roughly:
| Time to goal | Monthly SIP needed | Total invested |
|---|---|---|
| 10 years | ≈ ₹43,000 | ≈ ₹51.6 lakh |
| 15 years | ≈ ₹19,800 | ≈ ₹35.7 lakh |
| 20 years | ≈ ₹10,000 | ≈ ₹24.0 lakh |
| 25 years | ≈ ₹5,300 | ≈ ₹15.8 lakh |
The lesson is simple: time does more of the work than the amount. Starting five years earlier can halve the monthly contribution needed. Remember to inflate your goal too; something that costs ₹50 lakh today may cost well over ₹1 crore in 15 years at 6% inflation.
A middle path: STP
If you have a large sum and are nervous about investing it all at once in equity, you can park it in a liquid or short-duration debt fund and move a fixed amount into an equity fund every month through a Systematic Transfer Plan (STP) over 6–12 months. You earn debt returns on the waiting money while getting averaging benefits.
Tax on equity mutual funds
For equity-oriented funds, gains on units held for more than 12 months are long-term capital gains, taxed at 12.5% on gains above ₹1.25 lakh a year; shorter-term gains are taxed at 20%. Each SIP instalment is treated as a separate purchase with its own holding period. Debt fund rules are different. Tax rules change with Budgets, so check incometax.gov.in or your fund house for the current position.
Practical tips
- Match equity investments to goals at least five to seven years away.
- Do not stop SIPs when markets fall; that is when averaging works hardest.
- Choose direct plans if you are comfortable selecting funds yourself; expense ratios are lower.
- Review once a year, not every week.
- Keep an emergency fund in a savings account, FD or liquid fund before investing in equity.
Mutual fund investments are subject to market risks. This guide is educational and is not investment advice. For guaranteed-return options, see PPF vs SSY vs FD.
Plan your goal: enter your monthly amount in the free SIP Calculator and compare it with a lumpsum of the same total.
Frequently asked questions
How much will Rs 10,000 a month SIP become in 10 years?
At an assumed 12 percent annual return, about Rs 23.2 lakh on an investment of Rs 12 lakh. Actual returns depend on the fund and market conditions.
Is SIP better than lumpsum?
Neither is always better. Lumpsum tends to win in steadily rising markets when you already have the money; SIP reduces timing risk and suits monthly income. An STP is a useful middle path for large sums.
What is a step-up SIP?
A SIP whose monthly amount increases every year by a fixed percentage or amount, usually in line with salary growth. It can grow the final corpus substantially.
How are SIP returns measured?
Use XIRR, which accounts for the date of each instalment. CAGR is suitable for a single lumpsum investment.