How to Use the Long-Term SIP Calculator
Enter your monthly SIP and expected return, then set the tenure in years — or switch to months mode for exact month counts. Alongside the corpus you get: its value in today’s rupees at your assumed inflation, a decade-by-decade table showing how much each ten-year block added, and a comparison of the same SIP across 20, 25, 30, 35 and 40-year tenures.
Long-Term SIP Calculator Formula
M = A × ((1+i)ⁿ − 1) ÷ i × (1+i); Real value = M ÷ (1 + f)^(n/12)A, i, n= Monthly SIP, monthly return, tenure in monthsf= Assumed annual inflation (default 6%)
Example Calculation
₹10,000/month at 12% for 40 years (480 months):
Corpus ≈ ₹11.9 Cr on ₹48L invested; deflated at 6% inflation: 11.9 Cr ÷ (1.06)⁴⁰
≈ ₹11.9 crore nominal — worth ≈ ₹1.16 crore in today’s rupees
The final decade does the heavy lifting
The defining fact of a long SIP is invisible in a normal calculator and printed in a table on this one: growth is savagely back-loaded. Run ₹10,000 a month at 12% for 40 years and the decade table reads roughly ₹23 lakh, ₹95 lakh, ₹3.1 crore and ₹7.6 crore — the same instalment, the same return, yet the last ten years contribute two-thirds of the final corpus. Nothing special happens in year 31; the balance is simply large enough by then that 12% of it dwarfs everything the instalments add.
Two practical rules fall straight out of this shape. First, the most expensive years to stop a SIP are the last ones — abandoning the plan at year 30 of 40 forfeits the majority of the outcome, not a quarter of it. Second, early-years discouragement is mathematically guaranteed: after five years the corpus barely exceeds the deposits, and that is the formula working, not failing. The decade table exists to recalibrate expectations before the flat stretch tests them.
Nominal crores, real lakhs: the inflation adjustment
"₹11.9 crore in 40 years" is a genuinely misleading headline unless it is deflated, so this calculator does it by default. At 6% inflation, the price level multiplies about 10× over 40 years; the glittering ₹11.9 crore buys what ₹1.16 crore buys today. That is still an excellent outcome for ₹48 lakh invested — a real, inflation-beaten 2.4× — but it is a different retirement than the nominal figure implies, and planning against the nominal figure is how people arrive at 60 under-provisioned.
Use the real-value column to answer real questions: if a comfortable retirement needs the equivalent of ₹2 crore today, then a plan whose today’s-rupees projection reads ₹1.16 crore is 40% short, regardless of how impressive its nominal projection looks. Fixing the gap means some combination of a larger SIP, an annual step-up, or more years — and the third lever is the one this page is really about.
Five years earlier beats investing more, almost always
The tenure comparison table makes the case brutally: at ₹10,000 a month and 12%, a 35-year SIP reaches about ₹6.4 crore while a 30-year SIP reaches about ₹3.5 crore. The five extra years — ₹6 lakh of additional instalments — nearly double the outcome. To match the 35-year result in 30 years, the monthly SIP must rise to roughly ₹18,500: an 85% larger commitment, every month, for three decades, to buy back five years of compounding.
The asymmetry is the entire argument for starting imperfectly. A 25-year-old investing ₹5,000 a month typically retires ahead of a 32-year-old investing ₹12,000, despite investing far less money. If the choice is between starting now with a small amount or starting "properly" in a few years, the table says the delay is the expensive option — start small, then use an annual step-up to grow the instalment as income grows.
Making a 30-year plan survive contact with life
- Expect to change funds several times — the projection models the habit, not one scheme. Switching funds inside the plan is maintenance; stopping instalments is the failure mode.
- Re-run this page yearly with your real portfolio value and remaining months (months mode exists for exactly this) — volatility then becomes a small annual course-correction.
- Pair with the step-up SIP calculator: a 10% yearly increase turns the 40-year ₹11.9 crore projection into roughly ₹29 crore nominal, mostly from instalments you could afford anyway.
- For the drawdown side of the story — turning the corpus into monthly income at 60 — continue in the retirement calculator.
Frequently Asked Questions
What does a ₹10,000 SIP become in 40 years?
At 12%, about ₹11.9 crore on ₹48 lakh invested — but the same corpus is worth roughly ₹1.16 crore in today’s purchasing power at 6% inflation. Both numbers are true; plan with the second one.
Can I calculate a SIP for a specific number of months?
Yes — switch the tenure toggle to months and enter any count: 18 months for a near-term goal, 391 months to your exact retirement date. The maths is simulated month by month, so odd tenures are exact, not rounded to years.
Is 30 or 40 years a realistic SIP tenure?
It maps directly onto a working life: starting at 25 and retiring at 60 is a 35-year runway. No single fund needs to survive that long — investors switch schemes over decades — but the SIP habit itself, moved between funds as needed, is exactly what a 30–40 year projection models.
Why does the last decade add so much more than the first?
Compounding is back-loaded. In the 40-year example, years 1–10 add about ₹23 lakh while years 31–40 add roughly ₹7.6 crore — the final decade contributes more than the first three combined, despite identical instalments. This is also why pausing a mature SIP is far costlier than pausing a young one.
Should I reduce the assumed return for very long tenures?
Modestly, yes. Over 30–40 years, portfolios typically glide from equity-heavy to balanced as retirement nears, so a blended 10–11% is a more honest lifetime assumption than a pure-equity 12–13%. The tenure table updates instantly — check your plan at both.
How does inflation change what the corpus is worth?
At 6% inflation, prices roughly double every 12 years — over 40 years, today’s ₹1 buys what ₹10.3 will then. The "today’s rupees" column divides the projected corpus by that factor, converting a headline that flatters into a number you can actually plan retirement spending with.
Assumptions & Methodology
- Instalments at the start of every month, compounding monthly at a constant rate — identical conventions to the SIP calculator, so whole-year tenures match it exactly.
- Tenure can be entered in months (any count, e.g. 18 or 391) or years; the decade table groups completed years.
- “Today’s rupees” deflates the corpus by your assumed inflation rate over the full tenure; taxes and expense ratios are not deducted.
Sources
All calculations run in your browser and are provided for information only — they are not investment, tax or legal advice. Verify current rates and rules with the official source above before acting.