Return on investment (ROI)
Also known as: roi
Return on investment measures profit as a percentage of the money invested to earn it. Divide the gain or operating income by the investment base, and the result lets you compare opportunities of very different sizes on a common scale.
ROI answers a simple question: how much did this investment produce relative to what it cost? The basic form is ROI = net gain ÷ cost of investment, expressed as a percentage. Buy an asset for $50,000 and clear $6,000 after expenses, and the ROI is 12%. Because the result is a ratio rather than a dollar figure, a small project and a large one can be ranked side by side.
In management accounting, ROI is applied to a division or investment center as operating income ÷ average invested capital. It also decomposes usefully: ROI equals profit margin multiplied by asset turnover, so a manager can see whether a weak return comes from thin margins or from too much capital tied up in assets. The choice of investment base matters — gross book value, net book value, or current cost each produce a different number, and net book value inflates ROI over time as assets depreciate.
That sensitivity is ROI's main weakness. A manager evaluated on ROI may reject a project that earns more than the company's cost of capital simply because it would drag down the division's current average — the classic argument for pairing ROI with residual income, which measures income above a required capital charge in dollars rather than as a ratio. Plain ROI also ignores timing, so it is not a substitute for net present value on multi-year projects.
Investors use the same idea more loosely. Total return on a stock combines price appreciation with dividends received, divided by the amount invested; annualizing it makes holding periods of different lengths comparable.
CMA Part 1 tests ROI and residual income directly, including investment base and calculation issues, ACCA Financial Accounting covers it among profitability ratios, and the SIE touches the investor-facing version when it explains how dividends contribute to total return.
Key takeaways
- ROI expresses profit as a percentage of the amount invested, letting projects of different sizes be compared.
- In managerial accounting, ROI equals operating income divided by average invested capital, and decomposes into profit margin times asset turnover.
- The measure is sensitive to how the investment base is defined; net book value raises ROI as assets depreciate.
- ROI can push managers to reject good projects that would lower their average, which is why residual income is often reported alongside it.
- ROI ignores the timing of cash flows, so NPV remains the better tool for multi-year capital decisions.