SIP Calculator Assumptions: Real Returns vs Projected Returns

What the calculator is actually computing

The SIP calculator applies the standard future value of a growing annuity formula to project the maturity value of a series of regular (typically monthly) investments, compounded at an assumed annual rate of return over the specified investment tenure. The core formula is:

FV = P × [{(1+r)ⁿ − 1} / r] × (1+r)

Where P is the monthly SIP amount, r is the assumed monthly rate of return, and n is the total number of months. This is a pure compounding calculation — it does not, and cannot, predict actual future market performance.

The single most important assumption: the return rate you enter

Nominal returns vs real (inflation-adjusted) returns

Unless specifically toggled to an inflation-adjusted mode, the calculator's default projection shows the nominal future value — the actual rupee amount the corpus is projected to reach, without adjusting for the fact that a rupee at the end of a 20-year SIP tenure will have meaningfully less purchasing power than a rupee today. For genuinely evaluating whether a projected corpus will be "enough" for a real financial goal (retirement, a child's education), the inflation-adjusted (real) value of that corpus — what it will actually be able to purchase in today's terms — is the more meaningful figure, and can differ very substantially from the nominal number over long tenures.

What a reasonable return assumption looks like

The calculator does not itself dictate what return rate to assume — that is a user input reflecting their own expectation for the specific asset class/fund category being modelled (equity mutual funds, hybrid funds, debt funds each have very different realistic long-term return expectations). Using an unrealistically high assumed rate (extrapolating from a single strong recent year, for instance) will produce an overstated, misleading projection; using the calculator with a more conservative, historically-grounded long-term assumption for the relevant asset class produces a more useful planning figure.

What the calculator does not account for

• Expense ratios and other fund charges that reduce the investor's actual net return relative to the fund's gross/index-level return.
• Taxation on capital gains realised at redemption, which reduces the actual amount an investor takes home relative to the pre-tax projected corpus.
• Step-up SIPs (where the monthly investment amount increases periodically) — unless the calculator specifically has a step-up mode, the base calculation assumes a constant monthly SIP amount throughout the tenure.

How to use the projection sensibly

Treat the calculator's output as a useful order-of-magnitude planning tool for comparing different SIP amounts, tenures, or assumed-rate scenarios against each other — not as a specific number to anchor a firm financial commitment against, and revisit the projection periodically as actual returns and your own investment amount evolve, rather than treating a single calculation run years ago as still authoritative.