Publisher notes · reviewed 10 September 2026
How this SIP calculator actually works
The Toolioz SIP calculator projects the future value of equal monthly contributions using a monthly compound annuity, not a promised mutual-fund return. Changing the rate by two percentage points moves a ten-year plan by lakhs of rupees, which is why every figure on the page is tied to the inputs above.
What the number on screen is
A systematic investment plan (SIP) is a series of cash flows, usually monthly, into a mutual fund folio. The calculator does not look up live NAVs. It treats the expected annual rate as a constant and compounds it monthly. That is the same family of formula used in textbook future-value-of-an-annuity problems, with one extra (1 + i) factor so that each contribution is treated as being invested at the start of the month (annuity-due).
If the monthly rate i is zero, the tool simply multiplies the monthly amount by the number of months. Otherwise it uses M = P × [((1 + i)^n − 1) / i] × (1 + i), where P is the monthly contribution, i is the annual rate divided by 12, and n is years × 12. Step-up mode rebuilds the same annuity year by year, increasing P after each 12 months.
A worked check you can repeat by hand
Take ₹5,000 a month for 10 years at 12% a year. Then i = 0.01 and n = 120. Total invested is ₹6,00,000. The formula gives a projected value of about ₹11.62 lakh before tax, expense ratio, and exit load. Drop the rate to 10% and the same cash invested finishes near ₹10.33 lakh. The gap is not a rounding bug; it is compounding on a different i.
XIRR on a real folio will differ because NAVs jump, SIPs skip months, and dividends or STP switches change cash-flow dates. Use this page to size a contribution. Use the fund house statement and an XIRR function when you need a historical rate of return.
Tax and cost that the projection omits
Equity mutual fund units sold in India are currently taxed as short-term or long-term capital gains depending on holding period, with a stated annual LTCG exemption threshold that must be read from the Income Tax Department, not from this page. The calculator shows pre-tax corpus. Expense ratios also reduce the rate you actually earn: a 1% extra annual cost is closer to using 11% than 12% in the box above.
Direct plans omit distributor commission that regular plans embed in the expense ratio. Over 15 to 20 years that gap is visible in the same formula. None of this is personalised tax advice.
Worked examples
₹10,000 a month for 15 years at 12%
Invested capital is ₹18 lakh. The same annuity-due formula with n = 180 and i = 0.01 projects a little over ₹50 lakh before tax. A 10% annual step-up on the same starting P raises both invested capital and the ending value; the extra cash is new contributions, not free return.
Limits of this page
- The rate is an assumption, not a fund trailing return or a guaranteed yield.
- Cash flows are assumed on a fixed monthly grid with no missed SIPs.
- Inflation, tax, load, and expense ratio are not subtracted unless you lower the rate yourself.