How the ROI calculator works
Return on investment is the gain an investment produced measured against what it cost, written as a percentage. Put in what you invested, what came back, what it cost you along the way, and how long you held it, and this returns the ratio both before and after those costs.
Most ROI calculators ask for two numbers and a period. This one asks for three, and the third changes the answer more than people expect.
The formula
ROI = (gain from investment minus cost of investment) / cost of investment
Written the way Groww puts it, ((final value minus initial investment) / initial investment) x 100. Omni writes the same thing as (G - C) / C. Three different pages, one ratio.
The arithmetic is trivial. What isn't trivial is deciding which numbers go in it.
Nobody agrees what "cost" means
calculator.net names the problem outright: investors define cost and gain differently, depending on whether taxes, expenses and interim cash flows are counted. Two honest people can report very different ROIs on the same trade.
Groww goes as far as saying fees, taxes and transaction costs reduce the actual return, then offers nowhere to enter any of them. So the figure it hands back is always the gross one, and the reader is left to adjust it in their head.
Here's what that omission is worth on a small trade:
| Gross | After costs | |
|---|---|---|
| Invested | $10,000 | $10,000 |
| Fees and tax | not counted | $500 |
| Returned | $13,500 | $13,500 |
| Gain | $3,500 | $3,000 |
| Base it's measured against | $10,000 | $10,500 |
| ROI | 35% | 28.57% |
Six and a half percentage points, on $500. The costs hit twice: they shrink the gain and they enlarge the base, because money spent on fees is money the investment required of you.
ROI has no clock in it
The metric's other weakness is structural, and calculator.net calls it the biggest nuance with ROI: there's no timeframe involved. Doubling your money is 100% ROI whether it took three years or ten.
Annualising fixes it by spreading the total across the years:
Annualised ROI = (1 + ROI)^(1/years) - 1
| Doubling your money over | ROI | Annualised |
|---|---|---|
| 3 years | 100% | 25.99% |
| 5 years | 100% | 14.87% |
| 10 years | 100% | 7.18% |
Same headline, three completely different investments. That conversion is identical to the CAGR calculation, so on a single amount in and a single amount out, annualised ROI and CAGR are the same number.
A worked case
$10,000 into a holding sold three years later for $13,500, with $500 of brokerage and tax along the way.
The gross ROI is 35%, which is the figure every ranked calculator returns. After costs it's 28.57%. Annualised, the honest number is 8.74% a year, against the 10.52% a gross-only tool would imply. The gap between the number you'd quote at a dinner party and the number that describes what happened is nearly two percentage points a year.
What ROI can't tell you
Risk, most of all. A 12% ROI on a government bond and a 12% ROI on one speculative stock are the same number describing decisions that aren't remotely comparable, and nothing in the formula separates them.
It also can't handle money moving more than twice. ROI takes one amount in and one amount out. If you added to a position, took partial profits, or received dividends along the way, the ratio can't represent that faithfully and IRR or XIRR is the measure that can.
Nor does it say anything about opportunity cost. The capital was tied up for the whole period and could have been elsewhere, which is a comparison ROI simply doesn't make.
Results here are arithmetic on the numbers you entered, not financial advice. For decisions about your own money, speak to a licensed financial adviser. To annualise from a start and end value instead, use the CAGR calculator; to judge how long capital stays exposed, the payback period calculator answers that directly.
Frequently asked questions
What is the ROI formula? ROI = (gain from investment minus cost of investment) divided by cost of investment, usually shown as a percentage. Putting in $10,000 and getting back $13,500 is a $3,500 gain on a $10,000 cost, so 35 percent.
How do I calculate ROI after fees and taxes? Add the costs to what the investment required of you, then divide the remaining gain by that larger figure. On the same $10,000 to $13,500 trade with $500 of fees and tax, the gain falls to $3,000 and the base rises to $10,500, so ROI drops from 35 percent to 28.57 percent. That 6.43 point difference is the part almost every ROI calculator leaves out, because they give you nowhere to enter costs at all.
What counts as the cost of an investment? There is no single answer, and that is the metric's biggest weakness after its blindness to time. Some people count only the purchase price, others add brokerage, ongoing charges, and tax on the gain. Two honest people can report very different ROIs on the same trade. This tool shows the gross and net figures side by side so the choice is visible rather than buried.
What is annualised ROI and why does it matter? Annualised ROI spreads the total return across the years using (1 plus ROI) raised to the power of one over the years, minus one. It matters because plain ROI has no timeframe in it, so doubling your money reads as 100 percent whether it took three years or ten. Annualised, those are 25.99 percent and 7.18 percent a year, which are not remotely the same investment.
What is the difference between ROI and CAGR? ROI is the total ratio over the whole holding period and ignores time. CAGR is the steady annual rate that would produce that same result. The annualised ROI shown here is calculated the same way CAGR is, so on a single lump sum in and a single amount out, annualised ROI and CAGR are the same number.
What is the difference between ROI and IRR? ROI handles one amount in and one amount out. IRR handles a whole series of cash flows arriving at different times, and finds the rate that makes their net present value zero. If money went in or came out more than once, ROI cannot represent it properly and IRR or XIRR is the right tool.
What does ROI not tell you? Risk, above all. A 12 percent ROI on a government bond and a 12 percent ROI on a single speculative stock are the same number describing very different decisions, and nothing in the formula distinguishes them. It also says nothing about how much capital was tied up or what else you could have done with it.
Can ROI be negative? Yes. If the investment returns less than it cost, the gain is negative and so is the ROI. Getting $7,000 back from $10,000 is a negative 30 percent ROI, which annualised over two years is about negative 16.33 percent a year.
Sources
- calculator.net ROI calculator, which publishes the formula and names the definitional and timeframe weaknesses
- Omni Calculator ROI, which writes the ratio as (G - C) / C and separates ROI from return on equity
- Groww ROI calculator, an India-facing tool that names the cost drag without letting you enter it