What is ROI and how to calculate it
Updated on June 30, 2026 · by Rafael Rossi
ROI stands for Return on Investment. It answers exactly one question: how much came back, relative to what went in? It is the most quoted financial metric in the world, and also one of the easiest to use to fool yourself.
The formula
ROI = (gain − cost) ÷ cost × 100
Example: you put in $10,000 and took out $13,000. ROI = (13,000 − 10,000) ÷ 10,000 × 100 = 30%.
A negative ROI means a loss: −20% means 80% of what went in came back. And 100% ROI means the money doubled, not that it "came back whole" — a common confusion.
The hole in the middle: it ignores time
This is the most important limitation and the least discussed. Is a 50% ROI excellent or mediocre? There is no way to know without the holding period.
| Total ROI | Period | Annualised return |
|---|---|---|
| 50% | 2 years | 22.5% a year |
| 50% | 5 years | 8.4% a year |
| 100% | 10 years | 7.2% a year |
Look at the last row: doubling your money sounds spectacular, but 100% over ten years is 7.2% a year — below the long-run average of a plain index fund, with considerably more effort.
So whenever the period exceeds a year, the honest figure is the annualised return:
annualised = [(1 + ROI)1/years − 1] × 100
Be suspicious of anyone quoting a cumulative ROI without saying over how long. It is the politest way to inflate a result without lying.
The second hole: what counts as "cost"
Almost every optimistic ROI comes from an incomplete denominator. A property example with real numbers:
Bought at $300,000, sold at $390,000 four years later. Apparent ROI: (390,000 − 300,000) ÷ 300,000 = 30%. Now the costs nobody includes:
- Closing costs on purchase, around 6%: $18,000
- Agent commission on the sale, 6% of $390,000: $23,400
Real cost: $318,000. Net proceeds: $366,600. Gain: $48,600. The true ROI is 15.3% — half the apparent figure. Annualised over four years, 3.6% a year, before property taxes, insurance, maintenance and capital gains tax.
The rule: every cost required to obtain the return belongs in the denominator. Taxes, fees, commissions, shipping — and your own time, when it has a price.
What ROI does not measure
- Risk. Two investments with identical ROI can carry completely different probabilities of loss. ROI is measured after the fact; risk existed before it.
- Opportunity cost. An 8% annual return is only good if the safe alternative paid less over the same period.
- Liquidity. A return locked up for five years is worth less than the same return you can withdraw at any time.
- Scale. 200% on $500 is $1,000. 12% on $200,000 is $24,000. Percentages do not pay bills — absolute amounts do.
ROI on a personal decision
The formula works outside a balance sheet too, as long as you are honest about the denominator. The most searched case is a course or a degree.
A $24,000 program that produces an $800 monthly raise pays for itself in 30 months and, after five years, will have generated $48,000 — a 100% ROI over the period. But the real cost includes what almost nobody adds: the study hours. Two hundred hours you would have spent on paid work, or on the rest that sustains paid work, are a cost.
In cases like this the number rarely decides on its own — and it should not. Education opens doors that appear on no spreadsheet. ROI tells you the size of the bet, not which way to bet.
Frequently asked questions
What is a good ROI? There is no universal number. The useful benchmark is always comparative: the return has to beat the risk-free alternative over the same period, plus a premium proportional to the risk taken. For a marketing campaign the yardstick is different — you compare it against acquisition cost through other channels.
Is ROI the same as profit? No. Profit is an amount of money; ROI is a ratio. A business can have high profit and poor ROI (a lot of capital tied up) or small profit and excellent ROI (almost no capital at all).
How do I calculate marketing ROI? Use the profit generated, not the revenue. A campaign that cost $5,000 and generated $8,000 in revenue looks like 60% ROI, but if the product's gross margin is 40%, the profit was $3,200 — and the real ROI is −36%. Putting revenue in the numerator is the most expensive error in digital marketing.
What is the difference between ROI and payback period? Payback answers "how long until I get my money back" and ignores everything that happens afterwards. They are complementary: payback measures exposure, ROI measures result.