Measuring the return on investment (ROI) of advertising campaigns is essential for optimizing marketing budgets. Google Ads, Meta Ads, TikTok Ads: every dollar invested must generate more than a dollar in revenue. Two key indicators dominate: ROI (Return on Investment) and ROAS (Return on Ad Spend).
ROI measures the overall profitability of an investment taking into account total costs (not just the ad budget). ROAS measures only the revenue generated per dollar of ad spend, without accounting for other costs. E-commerce businesses often use ROAS as it's simpler to calculate in real time. A ROAS of 4× (400%) means every dollar invested generates $4 in revenue — but this can still be unprofitable if margins are thin.
📐 Formula
ROI = ((Revenue - Total costs) / Total costs) × 100 | ROAS = Revenue / Ad spend | CPA = Ad spend / Number of conversions
📊 Reference table
| Metric | Formula | Break-even | Target |
|---|---|---|---|
| ROI | (Revenue - Costs) / Costs × 100 | > 0 % | > 20–50 % |
| ROAS | Revenue / Ad spend | > 1× | 3× to 5× depending on margin |
| CPA | Ad spend / Conversions | < Customer value | < Unit margin |
| CTR | Clicks / Impressions × 100 | > 1–2 % | > 3–5 % |
| Conversion rate | Purchases / Visits × 100 | > 1 % | 2–5 % e-commerce |
💡 Practical examples
Example 1: Google Ads campaign — $500 budget, $2,000 revenue
ROAS = 2,000 / 500 = 4× (400%). If margin is 50%, net revenue = $1,000. Net profit = 1,000 - 500 = $500. ROI = (500/500) × 100 = 100%.
Example 2: minimum ROAS based on margin
If margin is 30%, minimum profitable ROAS = 1 / 0.30 = 3.33×. Below this threshold, every sale generated by the ad is unprofitable.
Example 3: optimize your target CPA
Average order value: $80. Margin: 40% → $32/sale. Maximum CPA to remain profitable: $32. If current CPA = $45 → campaign is unprofitable by $13 per conversion.