What ROI Measures
Return on investment is the plainest measure in finance: what you gained, divided by what it cost.
ROI = (Total proceeds − Total cost) / Total cost × 100
Its strength is that it applies to anything with a cost and a payoff — a share portfolio, a rental property, a marketing campaign, a degree. Its weakness is that it ignores time, and time is most of what separates a good investment from a bad one.
Why the Annualized Figure Is the Honest One
A 50% return is excellent over two years and mediocre over fifteen. The annualized return — the compound annual growth rate, or CAGR — strips the holding period out:
Annualized = (Proceeds / Cost)1/years − 1
| Total ROI | Held 2 years | Held 5 years | Held 15 years |
|---|---|---|---|
| 25% | 11.8% a year | 4.6% a year | 1.5% a year |
| 50% | 22.5% a year | 8.4% a year | 2.7% a year |
| 100% | 41.4% a year | 14.9% a year | 4.7% a year |
| 300% | 100.0% a year | 32.0% a year | 9.7% a year |
Reading down any column shows the trap in headline returns. A tripling over fifteen years — which sounds impressive — is 9.7% a year, close to what a plain index fund has historically delivered with far less effort.
Counting the Full Cost
ROI is only as honest as the cost figure. The commonly omitted items:
- Transaction costs — commission, spread, closing costs, transfer taxes. On property these routinely reach 6–10% of the price across a buy and a sell.
- Carrying costs — maintenance, insurance, property tax, storage, management fees.
- Tax on the gain — a 30% ROI before capital gains tax may be 22% after it.
- Money you added later — extra contributions belong in the cost, or the return is overstated.
Income received along the way — dividends, coupons, rent — belongs on the proceeds side. Leaving it out is the single most common reason a stock's true return is understated.
Where ROI Breaks Down
ROI assumes one amount in and one amount out. Where cash flows in and out repeatedly — a rental property with monthly rent and an occasional new roof — the internal rate of return handles the timing correctly and ROI does not. ROI also says nothing about risk: 12% from a Treasury ladder and 12% from a single speculative stock are the same number describing two entirely different decisions.
Frequently Asked Questions
What counts as a good ROI?
It depends entirely on the horizon and the risk. As a benchmark, the S&P 500's long-run average is roughly 10% a year before inflation, about 7% after. An investment that annualizes below that while carrying more risk is hard to justify.
Can ROI be more than 100%?
Yes. An ROI above 100% simply means the gain exceeded the original cost — the investment more than doubled.
Does ROI account for inflation?
No. It is a nominal figure. To convert to a real return, subtract the inflation rate from the annualized return; for a rough answer, 9% annualized at 3% inflation is about 6% real.