ROI Explained: How to Actually Calculate It and What People Get Wrong

The basic ROI formula is: ROI = (Net Profit / Cost of Investment) × 100. Net profit is the gain minus the original cost. So if you invest $10,000 and get back $13,500 total, your net profit is $3,500 and your ROI is (3,500 / 10,000) × 100 = 35%. This formula is time-agnostic — a 35% ROI over 1 year is very different from 35% over 5 years. For time comparisons, you'd use annualized ROI or other time-adjusted metrics like IRR (Internal Rate of Return).

It completely depends on the context, time frame, and risk level. The S&P 500 has historically returned about 10% annually before inflation. A savings account might offer 4–5%. A real estate investment might target 8–12% annual ROI. Venture capital investments target 20–30% annual returns but have high failure rates. For a marketing campaign, 300% ROI (every $1 spent returns $4 total) is often considered solid. A business investment with 15–25% annual ROI is generally considered good. The number is only meaningful compared to alternative uses of the capital and the associated risk.

All direct costs, and this is where ROI calculations often get inflated. For a marketing campaign: ad spend, agency fees, creative production, landing page development, and the staff time to manage it — not just the ad spend. For a software investment: license cost, implementation time, training time, and ongoing maintenance — not just the purchase price. For a business investment: initial capital, ongoing operational costs, opportunity cost of the capital (what else could it have earned), and time invested. Incomplete cost accounting is the most common way ROI gets overstated in business cases.