Project the future value of a monthly SIP / mutual fund investment.
FV = P × (((1+r)ⁿ − 1) / r) × (1+r), the standard future-value-of-annuity-due formula used for SIPs.
A Systematic Investment Plan invests a fixed amount at regular intervals rather than a lump sum at one moment. Two things drive the outcome. The first is compounding: returns earn returns, and because the earliest instalments compound for the longest, time in the market matters far more than the size of any single contribution. The second is rupee cost averaging — a fixed amount buys more units when prices are low and fewer when high, which smooths your average purchase price.
The figure a calculator produces assumes a constant rate of return. Real markets do not deliver that. Returns arrive unevenly, and the sequence matters, particularly near the end of your horizon. Treat the projection as a planning estimate, not a promise, and give more weight to the contribution and the duration than to the assumed return, since those are the two variables you actually control.
Be conservative. Long-run Indian equity returns have historically fallen in the low teens, but past performance does not guarantee future results and the realised figure for any particular period can be far lower. Modelling a lower rate and being pleasantly surprised is safer than planning around an optimistic one and falling short.
It is not safer in the sense of lower risk of loss — the underlying asset is identical. What it reduces is timing risk and the behavioural risk of investing everything just before a fall. Over long periods lump sums have often outperformed on average, simply because the money is invested for longer, but SIPs are far easier to sustain.
A step-up SIP increases your contribution by a set amount or percentage each year, usually in line with income growth. The effect is substantial: raising a contribution 10% a year can add materially to the final corpus compared with a flat amount, because each increase still has years left to compound.
Missing an instalment does not usually attract a penalty from the fund, though your bank may charge for a failed mandate. The real cost is the lost compounding on the amount not invested. Pausing is preferable to redeeming, since staying invested preserves the growth already accumulated.