Worked examples
The common benchmark
| ROAS | 4 |
| Equivalent ACOS | 25.0% |
| Revenue per $1 of ads | $4.00 |
4× ROAS ↔ 25% ACOS — profitable for products with pre-ad margins above 25%.
Aggressive growth spend
| ROAS | 2.5 |
| Equivalent ACOS | 40.0% |
| Revenue per $1 of ads | $2.50 |
2.5× ROAS ↔ 40% ACOS — only thick-margin or high-LTV products survive this.
Frequently asked questions
Why do the two metrics both exist?
Platform history. Google and Meta report return on ad spend because agency buyers think in returns on budget; Amazon reported advertising cost of sales because sellers think in cost percentages, like a fee. Sellers running both ecosystems constantly translate — this converter exists so a 30% ACOS Amazon campaign and a 3.3× ROAS Meta campaign are recognizably the same performance.
How do I convert ACOS back to ROAS?
Same reciprocal, flipped: ROAS = 100 ÷ ACOS. A 20% ACOS is a 5× ROAS, 25% is 4×, 33.3% is 3×, 50% is 2×. Because the relationship is a reciprocal rather than linear, small ACOS changes at the low end move ROAS dramatically: 10% → 12% ACOS drops ROAS from 10× to 8.3×.
Which metric should I standardize my reporting on?
Pick one and force every channel into it. ACOS compares naturally against margin — ads are profitable when ACOS is below your pre-ad margin percentage, a one-line health check. ROAS is more intuitive for budget planning (revenue = budget × ROAS). Many operators use ACOS for profitability reviews and ROAS for forecasting; mixing them mid-meeting is how bad decisions happen.
Is a higher ROAS always the better campaign?
Not when it comes from timidity. ROAS is highest on branded search and retargeting — audiences who were already coming. A 12× ROAS campaign harvesting existing demand can matter less than a 3× campaign profitably creating new customers. Judge campaigns on incremental profit at the margin, and use total volume alongside the ratio.
Related calculators
Part of the Advertising & ROAS collection.