Return on investment (ROI) is a straightforward ratio that measures how much you gained or lost relative to what you spent. It is one of the most widely used metrics in finance and business because it is simple, flexible, and works across nearly any category of spending or investment.
The ROI Formula
ROI = ((Gain - Cost) / Cost) × 100
Where:
- Gain = the total value returned (proceeds from a sale, revenue generated, money saved)
- Cost = the total amount invested or spent
A positive ROI means you came out ahead. A negative ROI means you lost money. The result is expressed as a percentage, which makes it easy to compare investments of different sizes.
What Counts as "Cost"
The most common mistake in ROI calculations is underestimating the true cost. Purchase price is usually just the starting point.
For a stock investment, cost includes not just the purchase price but also brokerage commissions and any advisory fees. For business equipment, cost includes the purchase price, installation, training, ongoing maintenance, and any downtime during the transition. For a marketing campaign, cost includes ad spend, creative production, agency fees, and staff time.
Understating costs inflates your ROI. When comparing investments, use a consistent definition of cost across all of them.
Worked Examples
Stock Investment
You buy $10,000 worth of stock. After several years, you sell for $14,500 and paid $100 in fees along the way.
Gain = $14,500 - $100 in fees = $14,400 net proceeds
Cost = $10,000
ROI = (($14,400 - $10,000) / $10,000) × 100 = 44%
Marketing Campaign
A company spends $8,000 on a digital ad campaign (including production costs). The campaign generates $22,000 in attributed revenue, and the cost of goods sold for those sales is $9,000.
Gain = $22,000 - $9,000 = $13,000 in gross profit
Cost = $8,000 campaign spend
ROI = (($13,000 - $8,000) / $8,000) × 100 = 62.5%
Business Equipment
A bakery purchases a commercial oven for $12,000. Over its useful life, the oven enables $5,000 in additional annual profit that would not otherwise be possible.
Over 5 years: Gain = $25,000. Cost = $12,000.
ROI = (($25,000 - $12,000) / $12,000) × 100 = 108%
Annualized ROI: Why Time Matters
A flat ROI percentage tells you nothing about how long it took to achieve that result. A 50% ROI over 10 years is far less impressive than a 50% ROI over 1 year.
Annualized ROI adjusts for time using this formula:
Annualized ROI = ((1 + ROI/100)^(1/years) - 1) × 100
For the stock example above (44% ROI over 4 years):
Annualized ROI = ((1 + 0.44)^(1/4) - 1) × 100
= (1.44^0.25 - 1) × 100
= (1.096 - 1) × 100
= 9.6% per year
Annualized ROI lets you compare any two investments on the same time-normalized basis.
What Counts as a Good ROI
Context determines what "good" means.
- In public equity markets, long-run average annual returns for a broad index fund have historically been in the 7-10% range (inflation-adjusted). An investment beating that benchmark consistently is considered strong.
- In real estate, cash-on-cash returns of 6-10% are commonly cited as solid for rental properties, though this varies widely by market.
- For marketing, a 3:1 revenue-to-spend ratio (roughly 200% ROI on gross revenue) is often cited as a baseline minimum, though margins must be considered.
- For business capital expenditures, the hurdle rate (the minimum acceptable ROI) varies by company but is often set at 10-20% annualized.
Comparing ROI to a specific benchmark or to alternative uses of the same capital is always more meaningful than treating any number as universally good or bad.
Limitations of ROI
ROI is useful precisely because it is simple, but that simplicity hides several things worth knowing.
It ignores risk. Two investments with identical ROI can have vastly different risk profiles. One might be nearly guaranteed; the other might have a high chance of returning nothing.
It ignores timing of cash flows. ROI treats a dollar received in year one the same as a dollar received in year five. Net Present Value (NPV) and Internal Rate of Return (IRR) handle this more accurately.
It can be gamed. By selectively defining what counts as "gain" or narrowing the cost basis, almost any investment can be made to look good on paper.
It ignores opportunity cost. An ROI of 15% may look fine in isolation, but if the next best use of that capital would have returned 25%, you are behind.
When to Use ROI vs. Other Metrics
Use ROI for quick comparisons and initial filtering. It is a useful first screen for any spending decision.
Use NPV when cash flows happen at different points in time and the time value of money matters.
Use IRR for comparing capital projects with different sizes and durations, or to compare against a company's cost of capital.
Use cash-on-cash return for real estate investments where you want to measure return on the actual cash you put in, accounting for financing.
Use the ROI Calculator to calculate simple ROI, annualized ROI, and total gain from any investment scenario without doing the math by hand.