SIP Calculator

How the SIP calculation works

Each monthly instalment is invested at the start of the month and then grows at the assumed monthly rate for the remaining months. For a flat SIP the closed-form future value is:

FV = P × [ ((1 + i)ⁿ − 1) ÷ i ] × (1 + i)

where P = monthly amount, i = monthly rate (annual rate ÷ 12 ÷ 100), and n = number of months (years × 12). When you set an annual step-up, the monthly amount rises by that percentage each year, so this tool simulates every month individually to stay exact. Estimated returns = Total value − Invested amount, and the wealth ratio is total value ÷ invested amount.

Rupee-cost averaging: how investing on autopilot beats timing the market

The single biggest behavioural advantage of a SIP is that it removes the temptation to time the market. Because you invest the same fixed rupee amount every month regardless of the price, your money automatically buys more units when the market is down and fewer units when it is up. Over a full cycle this pulls your average cost per unit below the simple average of the prices you paid — a phenomenon called rupee-cost averaging.

The table shows a ₹10,000 monthly SIP across six months of a volatile market. The fund's NAV (net asset value, the price of one unit) swings from ₹100 down to ₹50 and back up:

You invested ₹60,000 and accumulated 685 units, so your average cost was ₹60,000 ÷ 685 = ₹87.59 per unit — noticeably below the simple average NAV of ₹96.67. You did nothing clever; the discipline of buying a fixed amount did the work, automatically loading up in month 5 when units were cheapest. At the month-6 NAV of ₹125, your holding is worth 685 × ₹125 = ₹85,625. Mathematically, rupee-cost averaging delivers the (quantity-weighted) harmonic mean of the prices, which is always less than or equal to the arithmetic mean — that is the small, durable edge a SIP gives you for free.

One honest caveat: rupee-cost averaging reduces the risk of investing a large sum at exactly the wrong moment, but it is not a guarantee of profit. In a market that only ever falls, you would still lose money — just less than a single lump sum bought at the top.

Why time matters more than the rate of return

Compounding means your returns themselves start earning returns. In a SIP, each instalment buys units, those units appreciate, and the gains stay invested to grow on top of the original money. The effect is gentle for the first few years and then accelerates sharply — which is why the length of time invested usually matters more than squeezing out an extra percent of return. The classic illustration uses two investors, both assuming a constant 12% a year:

• Priya starts early and stops. She invests ₹5,000 a month from age 25 to 35 — just 10 years, ₹6,00,000 in total — then never adds another rupee, leaving the corpus invested until she turns 60.
• Rahul starts late and never stops. He invests ₹5,000 a month from age 35 all the way to 60 — 25 years, ₹15,00,000 in total.

At an assumed 12%, Priya's ₹6 lakh grows to roughly ₹2.3 crore by age 60, while Rahul's ₹15 lakh — two and a half times the money, invested for far longer — reaches only about ₹95 lakh. Priya ends with more than twice as much from a fraction of the contributions, purely because her early money had a decade's extra head start to compound. The lesson is not that you should stop investing at 35; it is that the most valuable rupee you will ever invest is the one you invest today. Starting a small SIP now usually beats waiting until you can afford a large one.

Illustrative only, at a constant 12% return. Real mutual-fund returns vary year to year and are not guaranteed.

Step-up (top-up) SIPs: let your investments grow with your income

A flat SIP keeps the same instalment for years, but your salary rarely stands still. A step-up SIP (also called a top-up SIP) raises the monthly amount by a fixed percentage every year — typically 5–15%, roughly in line with annual pay rises. Because the increase compounds, the later, larger contributions still have years left to grow. Use the Annual step-up (%) field above to model it exactly.

Take a ₹10,000 SIP over 10 years at an assumed 12%:

• Flat SIP: you invest ₹12,00,000 in total and it grows to roughly ₹23.2 lakh.
• 10% annual step-up: the instalment rises from ₹10,000 to about ₹23,580 by year 10. You invest ₹19,12,000 in total, and the corpus grows to roughly ₹33.7 lakh.

The step-up produces a meaningfully larger pot — but note why: most of the gain comes from contributing more money (₹19.1 lakh versus ₹12 lakh), not from any magic in the structure. A step-up SIP is best understood as a painless way to keep your saving rate constant as a share of a rising income, rather than letting inflation quietly shrink the real value of a frozen instalment. Even a modest 10% step-up can be the difference between hitting a long-term goal and falling short of it.

SIP vs lump sum: which suits which kind of money

The right choice depends less on which is "better" and more on the money you are deploying. A lump sum invests everything at once, so it puts the maximum amount to work for the longest time — ideal when markets then rise steadily, but punishing if you happen to invest just before a downturn. A SIP spreads the same money across many entry points, smoothing out the timing risk through rupee-cost averaging and matching the monthly rhythm of a salary.

In practice:

• If your money arrives monthly (from a salary), a SIP is the natural fit — you simply invest as you earn.
• If you receive a windfall (a bonus, an inheritance, a maturity payout), you face a real choice. Historically, investing a lump sum immediately has come out ahead more often than not, because markets rise more often than they fall. But the worst-case outcome of a lump sum — investing it all at a peak — is far more painful, which is why many investors split a large windfall into a series of investments over 6–12 months (a strategy sometimes called STP, a systematic transfer plan, moving money gradually from a liquid fund into equity).

There is no universally correct answer, and many disciplined investors run a monthly SIP for their regular savings and deploy windfalls as lump sums. What matters far more than the SIP-versus-lump-sum debate is staying invested through the inevitable downturns.

Measuring SIP returns correctly: why XIRR beats a simple percentage

Because a SIP invests on many different dates, you cannot judge it with a single "total return" percentage — each instalment has been invested for a different length of time. The correct measure is XIRR (extended internal rate of return), the annualized rate that accounts for the exact date and size of every cash flow. Most fund platforms and a spreadsheet's XIRR() function report it for you.

This is why a SIP's headline number can look confusingly modest: if you invested steadily for 10 years and your corpus is up 60% overall, the annualized XIRR is far higher than 6%, because the money you added in year 9 was only invested for one year. This calculator projects a corpus at a single constant assumed rate, which is perfect for planning; XIRR is what you use afterwards to measure how your real, market-driven SIP actually performed.

SIP best practices and common mistakes

• Do not stop a SIP when markets fall. A downturn is exactly when your fixed instalment buys the most units — pausing throws away the core benefit of rupee-cost averaging.
• Give it time. Equity SIPs are designed for long horizons (ideally 7 years or more). Over short periods, returns can easily be negative; over long periods, the odds improve markedly.
• Mind the expense ratio. A fund's annual expense ratio is deducted from returns every year. Over decades, the gap between a 0.5% index fund and a 2% active fund compounds into a large sum — this calculator's assumed rate should be a net-of-cost estimate.
• Match the fund to the horizon. Equity funds suit goals 7+ years away; debt or hybrid funds suit shorter goals where a market fall just before you need the money would hurt.
• Step up with your income rather than starting a second SIP each year — it keeps your saving rate steady against inflation.
• Use realistic, conservative return assumptions. Planning at 10–12% for equity is reasonable; planning at 18% sets you up for disappointment.

Direct vs regular plans: a small fee that compounds into a lot

Every mutual fund scheme comes in two variants. A regular plan pays a commission to the distributor or agent who sold it, baked into a higher annual expense ratio. A direct plan cuts out that commission — you buy straight from the fund house — so its expense ratio is lower, often by 0.5% to 1% a year. The portfolio, the fund manager and the strategy are identical; only the cost differs.

That gap sounds trivial, but it is deducted every year from your entire balance, so it compounds against you exactly the way your returns compound for you. Over a long SIP the difference can run into lakhs of rupees — as a rough sense of scale, a 1% higher annual fee can quietly shave well over 10% off a 20-year corpus. When you set the assumed return in this calculator, remember it should be a net-of-cost figure, and that switching to a direct plan is one of the very few ways to raise your real return with no extra risk at all.

What this calculator does — and does not — show

This tool projects what a SIP would grow to if it earned a single, constant annual return for the whole period. Real markets never move in a straight line: equity mutual funds rise and fall, sometimes sharply, and the actual outcome depends on the precise path of returns over your investment window. The figures here are an estimate for planning, not a promise. Mutual fund investments are subject to market risk; as SEBI requires every fund to state, past performance does not guarantee future returns. Read the scheme documents and, if you are unsure, consult a SEBI-registered investment adviser before investing.