What is a good ROI? Benchmarks, the annualization trap, and honest math

“What’s a good ROI?” is really three questions wearing one trench coat: how is the number computed, over what time period, and compared to what? Most bad conclusions about returns come from skipping the second one. This guide covers the formula, the annualization step that makes comparisons honest, what long-run market history actually says, and the deductions — inflation, fees, taxes — that separate the headline number from what you keep. It is educational only, not investment advice; for decisions about your own money, consult a licensed financial adviser.

How do you calculate ROI?

Return on investment is the simplest performance metric there is:

ROI = (final value − initial cost) ÷ initial cost × 100

Put $10,000 in, take $12,500 out: (12,500 − 10,000) ÷ 10,000 = 25%. Two rules keep the number honest. First, the denominator is the totalcost — purchase price plus commissions, closing costs, renovations, whatever it actually took. Second, the final value includes every cash flow received along the way: dividends, rent, interest. Quoting a stock’s price gain while ignoring its dividends understates ROI; quoting a rental property’s sale price while ignoring five years of repair bills overstates it.

The annualization trap

Here is the mistake that invalidates most casual ROI comparisons: ROI has no time dimension.A 25% ROI earned in one year and a 25% ROI earned over eight years produce the same number, and they are wildly different outcomes. Comparing raw ROIs across different holding periods is meaningless — it’s comparing speeds by looking only at distance travelled.

The fix is to annualize, which for a single lump sum means computing the compound annual growth rate (CAGR):

CAGR = (final ÷ initial)^(1 ÷ years) − 1

Note the exponent: because gains compound, you can’t just divide the total ROI by the number of years. A 50% ROI over five years is not 10% a year — it’s (1.50)^(1/5) − 1 ≈ 8.45% a year. The naive division always overstates the per-year rate, and the gap widens with longer periods and bigger gains. (This is the same mechanism covered in our compound interest guide, run in reverse.) Once both investments are stated as annualized rates, and only then, they can be compared.

What is a good return on investment? The benchmarks

With annualized numbers in hand, “good” needs a yardstick, and the standard one is the long-run return of a diversified stock index. Aswath Damodaran’s widely cited dataset at NYU Stern, which tracks US stocks, bonds, and Treasury bills back to 1928, puts the S&P 500’s long-run average at roughly 10% per year in nominal terms — about 7% per year after inflation. Treasury bonds have historically returned around half that, and cash-like Treasury bills less still.

Two caveats keep these figures honest. They are very long-run averages: individual years have ranged from roughly −40% to +50%, and even full decades have landed well above or below the average. And they are US figures from an unusually successful century of US markets; they describe the past, not a promise about any future period. Used carefully, though, they anchor the common questions: an annualized 10% is around the historical average for equity-level risk — solid, not extraordinary. An annualized 15–20% sustained over many years is exceptional; the best-known professional track records live in that range. And a low-single-digit annualized return took equity risk to earn what safer assets have often paid.

Nominal vs real: subtracting inflation

ROI is a nominal figure — it counts dollars, not purchasing power. To see what a return actually bought you, deflate it with a price index such as the BLS Consumer Price Index:

real ≈ (1 + nominal) ÷ (1 + inflation) − 1

A 6% year against 3% inflation is a real gain of about 2.9%. A 4% year against 8% inflation is a real loss of about 3.7%, positive ROI notwithstanding. This is why the equity benchmark is quoted both ways: ~10% nominal, ~7% real. Over long horizons the gap compounds enormously — our inflation calculator makes the erosion concrete.

ROI vs IRR vs ROE, in one paragraph each

IRR(internal rate of return) is the annualized rate that accounts for the timing of every cash flow. When money goes in and comes out at different times — a rental property with monthly rent, a business with staged investments — CAGR’s single-lump-sum assumption breaks down and IRR is the right tool.

ROE(return on equity) sounds similar but measures something else entirely: a company’s net income divided by its shareholders’ equity. It grades how efficiently a business uses its capital, not what an investor earned by holding it.

ROI remains the right first pass for a simple in-and-out investment — just annualize it before comparing.

Fees and taxes: the quiet subtractions

Every published benchmark is gross of the costs you personally pay. A 1% annual management fee doesn’t turn a 7% real return into 6% and stop there — compounded over 30 years it consumes roughly a quarter of the final balance. Capital gains tax takes its cut at sale, and in many jurisdictions short holding periods are taxed at higher rates than long ones. When judging your own ROI against a benchmark, compute it net: after commissions, fund fees, transaction costs, and the taxes actually owed. Most “I beat the market” claims dissolve at this step.

When a high ROI is a red flag

Returns are compensation for risk, so a quoted return far above the historical equity range should raise the question what risk is paying for this?— and if no one can answer, that is itself the answer. Consistent double-digit monthly returns, “guaranteed” 20%+ annual returns, and strategies whose results never have a down period are the classic profile of fraud; the SEC’s investor-education materials at Investor.gov list too-good-to-be-true returns as the leading warning sign. Legitimate high returns exist, but they arrive with visible volatility and real chances of loss. A smooth line going up and to the right at triple the market rate is not an opportunity — it’s a lure.

Short version: compute ROI with all costs in and all cash flows counted, annualize it before comparing anything, judge it against the ~10% nominal / ~7% real long-run equity record rather than a fantasy number, then subtract inflation, fees, and taxes to see what you actually kept. And treat any return that makes those benchmarks look boring as a claim to verify, not a deal to chase.