"I made forty percent" is one of the least useful sentences in personal finance. Over eight months it is a remarkable result. Over eight years it is worse than a fixed deposit. Return on investment only becomes a decision-grade number once you divide it by the time it took to earn, and that single step is what most people skip.
Three questions, one calculator
Return on investment is used loosely to mean several different calculations, and using the wrong one produces confident, wrong conclusions. This tool separates the three that matter most to Indian investors.
Buy and sell looks backwards at something you have already done. You supply what you put in, what it is worth now or what you sold it for, and how long you held it. You get the absolute return and, more importantly, the compound annual growth rate.
Lump sum growth looks forward from a single investment made today at a return rate you assume. Monthly SIP looks forward from a recurring monthly contribution, with an optional annual step-up that mirrors a salary increment. Both are projections, and their honesty depends entirely on the honesty of the rate you enter.
Why CAGR is the number that travels
Absolute return answers "how much did it grow?" CAGR answers "how fast?" Only the second one lets you compare across holdings.
Consider two results. A property bought for forty lakh and sold for eighty lakh has doubled — a 100% absolute return. A mutual fund holding that turned two lakh into three lakh has grown 50%. The property looks like the clear winner until you learn the property was held for fourteen years and the fund for three. The property compounded at roughly 5.1% a year; the fund at roughly 14.5%. CAGR reverses the ranking, and CAGR is right.
This is the everyday value of the tool. Whenever someone quotes a return without a time period attached, the number is incomplete. Put both into this calculator and the comparison becomes real.
Where CAGR breaks, and what replaces it
CAGR assumes one amount in at the start and one value at the end. The moment money moves in or out midway, it stops being accurate.
If you added to a position across three years, took partial profits, or ran a SIP, your true return is an XIRR — a rate that weights each cash flow by the date it occurred. Applying CAGR to a SIP by dividing the final corpus by the total invested is a common and significantly misleading error, because it treats a rupee invested last month as though it had been compounding from the beginning. Use the buy-and-sell mode for single-entry, single-exit positions, and treat SIP projections as projections rather than as realised returns.
The rule of 72, for sanity-checking
Divide 72 by an annual return to get the rough number of years for money to double. At 12% that is about six years; at 8%, about nine. If a projection or a pitch implies doubling far faster than the rule of 72 suggests for a plausible rate, something in the assumptions deserves a second look.
Projections are assumptions wearing a suit
The forward-looking modes will produce a large, precise-looking number. That precision is an illusion created by the calculator, not a property of the future. The corpus you see is the arithmetic consequence of the rate you typed, nothing more.
Two habits make projections useful rather than misleading. First, always run three rates — cautious, moderate and optimistic — and plan around the cautious one. If a goal is only reachable at the optimistic rate, it is not funded; it is hoped for. Second, remember that no real market delivers the same return every year. A fund averaging 12% over fifteen years might return 30% in one year and lose 20% in another. The smooth curve in the table is an average, not a path.
What a step-up SIP actually does
Set the step-up to 0% and note the corpus. Set it to 10% and look again. On a fifteen or twenty year horizon the difference is usually large enough to be surprising.
The mechanism is simple: a step-up adds money in the early and middle years, when there is still a long runway for compounding. This is the same principle that makes early prepayment powerful on a loan, running in the opposite direction. It also has a behavioural advantage — raising a SIP by a fixed percentage each year, timed to your increment, is far easier to sustain than trying to invest a lump sum from a bonus you have already mentally spent.
Nominal, not real
Every figure here is in today's rupees at face value. Inflation is not deducted, tax on gains is not deducted, and expense ratios, brokerage and exit loads are not deducted. A crore in twenty years will not buy what a crore buys now. A rough way to see the purchasing-power figure is to subtract your inflation assumption from your return assumption before you run the projection — the result is a smaller, more sobering, more useful number.
Reading the compounding table
The year-by-year table below the calculator shows something that a single final figure hides: compounding is unimpressive for a long time and then it is not.
In the early years of a SIP, growth is small compared to your contributions, and it can feel as though little is happening. Somewhere in the middle, the growth column overtakes the amount you add each year, and from that point the corpus is being driven more by the returns on money already invested than by new money going in. Find that crossover row. It is the single best illustration of why time in the market does more work than the size of any individual contribution — and why stopping a SIP during a bad stretch is so costly.
Measuring a single position properly
For any holding you entered once and exited once — an allotment you sold, a stock you bought and held, a fixed deposit that matured — the buy-and-sell mode gives you the clean answer. Two details are worth getting right when you enter it.
First, use your total cost, not the headline price. Brokerage, stamp duty, transaction charges and GST all reduce your real return, and leaving them out flatters the result. Second, use the net proceeds on the exit side, after exit load and charges but before tax, and be accurate about the holding period — rounding eighteen months up to two years understates your CAGR by a meaningful margin.
Do this consistently across every position you close and a pattern usually emerges within a year or two. Some holdings that felt like wins turn out to have compounded at single digits because they took four years to get there. Others that felt unremarkable turn out to have been the strongest performers per unit of time. That is uncomfortable information, and it is exactly the information worth having.
Using the result honestly
Backwards-looking numbers tell you what happened, and they are worth calculating properly for every position you close. Knowing that a holding you were pleased with actually compounded at 7% is useful information, even when it is unwelcome.
Forward-looking numbers are planning tools, not promises. They are best used to answer structural questions: is this monthly amount roughly in the right range for this goal, or is it off by a factor of two? Does this horizon need a different approach entirely? Those are questions a projection answers well. What it will never answer is what any specific investment will actually do — and no calculator, however carefully built, changes that.