ROI calculator
Enter how much you invested and the final value (or revenue): calculate the return on investment as a percentage and the profit.
What is ROI
ROI (Return On Investment) measures how much an investment earns relative to what you spent: ROI = (final value − invested) ÷ invested × 100.
Example
You invest €1,000 and get back €1,250: the ROI is +25%. A negative ROI means you lost relative to what you invested.
ROI does not say how long it took
This is the most important limit and the most ignored. A 25% ROI earned in six months and one earned in ten years are the same number, but not the same deal: the first, repeated, doubles the capital in a little over three years; the second loses to inflation. To compare investments of different length you need the annualised return, which spreads the gain over the years, not the raw ROI.
It is why the figures advertised for certain investments are almost always total ROIs over long periods: a «+60%» without the words «in ten years» next to it is half an answer.
What really goes into the amount invested
The denominator is where people cheat, often without noticing. Every outflow tied to the operation counts, not just the purchase price: fees, taxes, shipping, the advertising it took to sell, packaging, the share of stock unsold or returned. A margin that looks excellent on the list price becomes thin once the side costs come in.
And there is a cost that appears on no invoice: time. If a side activity earns 2,000 a year but takes two hundred hours, the return on the money can be splendid and the return on your life much less so.
The number everything else should be measured against
A positive ROI does not mean the operation was good: it means it returned more than zero. The honest comparison is with what you would have got by doing nothing in particular, that is with a boring, liquid investment. If a complicated, risky project returns less than that baseline, the risk was taken for nothing.
Inflation comes in here: +3% in a year when prices rose 4% is a loss of purchasing power, even though the account shows a bigger number than before.
Nearby tools
For returns over time there is Compound interest; to see what yesterday's money is worth today, Inflation calculator. Anyone selling a product will find in Break-even point how many units cover the costs, and in VAT calculator the step between price with and without tax.