SIP calculator
What a monthly investment grows to over time — with an annual step-up if you increase your contribution, and an inflation-adjusted figure showing what it will actually buy.
Why the fourth number matters most
Most SIP calculators show you three figures and stop. The one they leave out is the one that decides whether the plan works: what the maturity amount will actually buy.
₹5,000 a month for 20 years at 12% comes to about ₹50 lakh. That sounds transformational. At 6% inflation, its purchasing power in today's money is closer to ₹15.6 lakh — still good, but a third of the headline. Any plan built on the big number is built on an illusion.
The adjustment is simply:
today's money = maturity ÷ (1 + inflation)^years
What step-up does
A step-up SIP raises your monthly contribution by a fixed percentage each year, usually matching a pay rise. It matters far more than people expect, because the early increases compound for almost the whole period.
Set the step-up to 10% and compare. On ₹5,000 a month for twenty years at 12%, a 10% annual step-up takes the maturity value from about ₹50 lakh to ₹99 lakh — almost exactly double — for contributions that never feel like a jump. Your first year is unchanged, and each rise is proportional to what you were already paying.
How it is calculated
For a level SIP, the standard formula is the future value of an annuity due — payments made at the start of each month:
M = P × ( ((1 + i)ⁿ − 1) / i ) × (1 + i)
- P — monthly investment
- i — monthly rate, which is the annual rate ÷ 12 ÷ 100
- n — number of months
So ₹5,000 a month for 10 years at 12% gives i = 0.01 and n = 120, and works out at ₹11,61,695. You can check this page against that figure.
This calculator does not use the closed formula. It steps through month by month — adding your contribution, then applying one month's growth — because that is the only way to handle a step-up correctly, and it produces exactly the same answer as the formula when the step-up is zero. The monthly loop is also easier to verify: the sum of contributions is reported separately, so you can see the two halves.
Where the numbers come from, and where they don't
The return figure is yours to choose, and it is a guess. No calculator can know it. Indian equity mutual funds have historically returned somewhere in the low teens over long periods, which is why 12% is the conventional default — but past returns are not a promise, and a period that includes a bad decade will not look like the average.
If you want an honest range, run it three times: at 8%, at 12% and at 15%. The spread between those is the real uncertainty in the plan, and it is much wider than most people expect.
Common questions
Does this match SBI's or Groww's calculator?
It should, to within rounding. They use the same annuity-due formula. If a figure differs by more than a rupee or two, check whether the other calculator applies growth at the end of the month rather than the start — that changes the answer by roughly one month's interest.
Is the return taxed?
Yes, and this does not account for it. Capital gains treatment depends on the fund type and how long you hold, and the rules change. The maturity figure here is before any tax.
Can I use it for a lumpsum instead?
Not directly — this models a monthly contribution. For a single lumpsum the calculation
is simply amount × (1 + annual rate)^years, with no monthly compounding
involved, which any ordinary calculator will do.
What if I stop paying partway through?
The invested amount stops growing by contribution but keeps compounding. This calculator assumes you pay every month for the full period; a stopped SIP will finish lower.
Do my figures go anywhere?
No. What you invest, for how long and at what return stays in your browser. There is no account, nothing tracking the amounts you model, and no server doing the maths — you can disconnect from the internet after the page loads and it still projects.