Return on Investment (ROI)

ROI is the ratio of the gain from an investment relative to its cost. If you spend $10,000 on a marketing campaign and it generates $40,000 in new revenue with $25,000 in associated costs, the net gain is $15,000 and the ROI is 150%. Simple in concept, but meaningfully useful only when you're clear about what goes into the numerator and denominator.

Why ROI is frequently misused

The most common mistake is using revenue instead of net gain in the numerator. If you spend $10,000 on equipment and it generates $10,000 in new revenue, your ROI is not 100% — it's whatever that $10,000 in revenue leaves after direct costs. Gross revenue is almost never the right numerator. Net profit or cash flow from the investment is.

ROI and time

A 50% ROI over one year is very different from a 50% ROI over five years. Basic ROI doesn't account for time — which is why more sophisticated analyses use annualized ROI or discounted cash flow modeling for long-term investments. For a small business evaluating a piece of equipment or a marketing spend, annualizing gives a more useful comparison: "this equipment pays for itself in 14 months" is more actionable than "ROI is 86%."

When ROI is the right question

ROI is most useful for comparing discrete investments where the costs and returns are reasonably estimable: equipment, marketing spend, a new hire, a software tool. It's less useful for evaluating the overall health of the business — for that, you want metrics like pre-tax profit margin, LER, and free cash flow.