How to Evaluate an Investment with ROI (and Its Blind Spots)
ROI answers a deceptively simple question: for every dollar in, how many came out? Its simplicity is its power and its danger — the same simplicity hides time, risk and cost if you let it.
- ROI = (final value − amount invested) ÷ amount invested. Annualize it whenever the holding periods differ.
- Include every cost in the invested amount: fees, taxes, maintenance, your own time for projects.
- ROI ignores risk entirely — a 15% ROI from a savings product and a 15% ROI from a crypto bet are not equivalent offers.
The formula and the time trap
ROI = (final − initial) ÷ initial × 100. A $10,000 investment ending at $16,000 is a 60% ROI. Sounds great — until you learn it took nine years, which annualizes to about 5.4%, below the historical market average.
This is the time trap: absolute ROI is only comparable between investments held for the same period. The moment timeframes differ, you need the annualized figure (CAGR) to compare fairly. Our ROI calculator shows both numbers side by side for exactly this reason.
The cost trap
The invested amount must include everything it cost to get the return: trading fees, taxes due on exit, renovation costs on a rental, and for side businesses, a fair price for your own hours.
Excluding costs is how bad projects look viable. A rental property with a 30% ROI on purchase price can be a 12% ROI once closing costs, taxes and maintenance are loaded in — still fine, but a different decision.
The risk blind spot
ROI has no risk dimension. A 10% ROI from a treasury ladder and a 10% ROI from a leveraged venture are identical on paper and opposite in reality. The professional correction is to demand a risk premium: risky investments should clear the safe alternative by a wide margin, not a hair.
A practical benchmark ladder: savings accounts sit near the risk-free floor, public equities historically run 7–10% annualized, and anything riskier than equities should promise meaningfully more to justify the added chance of loss.
A working checklist
Before committing: compute the annualized ROI, load every cost into the denominator, compare against what the same money earns risk-free, and stress-test the final value assumption. If the deal only works at the optimistic number, it does not work.
Try the calculators
ROI Calculator
Enter what you put in and what it is worth now to see your total return on investment (ROI) and the annualized (per-year) return.
CAGR Calculator
Compute the compound annual growth rate (CAGR) — the smoothed per-year growth rate that turns a beginning value into an ending value over a number of years.
Frequently asked questions
What is a good ROI?
Depends on risk and timeframe. 7–10% annualized is the historical equity benchmark; anything above it should be interrogated for hidden risk.
Should ROI include dividends and rent?
Yes — add all income received to the final value. Ignoring income streams understates total return on any yield-producing asset.