Calculate Return on Investment: Formula, Example & Guide

The return on investment (ROI) shows in a single number how efficiently you used your capital. Formula: ROI = (Revenue - Investment costs) / Investment costs × 100. A positive percentage means profit; negative means loss.

ROI formula and example

Example: You spend €2,000 on a Google Ads campaign and generate €6,000 in revenue. Net result: €4,000. ROI = 4,000 / 2,000 × 100 = 200%. For every euro invested, you earned two euros profit.

Common mistakes

The most frequent error is incomplete cost capture — missing internal working hours, tool licenses or agency fees. Always include all direct and indirect costs for an accurate ROI.

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