What are marginal metrics?
Marginal metrics look at the next euro you're about to spend instead of the euros you've already spent. Where traditional ROAS, CPA, CPC and POAS tell you how your campaigns performed so far, marginal metrics answer a more forward looking question:
"If I spend one more euro on this campaign, what return or cost can I expect?"
Which marginal metrics does Billy Grace offer?
Marginal ROAS (Return on Ad Spend): higher = better
Marginal CPA (Cost per Acquisition): lower = better
Marginal CPC (Cost per Click): lower = better
Marginal POAS (Profit on Ad Spend): higher = better
Note: Marginal POAS is only available for accounts with an active Channable integration. If you don't have Channable connected, this option will not appear in your automation settings.
Average Metrics vs. Marginal Metrics
| Average ROAS/CPA/CPC/POAS | Marginal ROAS/CPA/CPC/POAS |
Looks at... | All euros spent so far | The next euro you’ll spend |
Helps with... | Performance review | Smart budget allocation |
Managing diminishing returns
Every campaign hits a point of diminishing returns: where spending more yields less return.
Here’s how that typically looks for ROAS:
🟢 Low spend zone: Each euro earns high returns (e.g., €13.39 per €1)
🟡 Medium spend: Returns are still good, but lower (e.g., €5.52 per €1)
🔴 High spend: Each extra euro barely adds value (e.g., €1.13 per €1)
See the plots below for how this looks in practice for each metric.
For CPA:
🟢 Low spend: Low CPAs (great efficiency) (e.g., €1.62 per €1)
🟡 Medium spend: CPA increases slightly (e.g., €7.18 per €1)
🔴 High spend: CPA climbs steeply: each extra euro costs more to convert (e.g., €9.33 per €1)
For CPC:
🟢 Low spend: Low CPCs (great click efficiency) (e.g., €0.17 per €1)
🟡 Medium spend: CPC increases slightly (e.g., €0.47 per €1)
🔴 High spend: CPC climbs steeply: each extra euro buys fewer clicks (e.g., €0.60 per €1)
For POAS:
🟢 Low spend zone: Each euro generates high profit returns (e.g., €4.17 per €1)
🟡 Medium spend: Profit returns are still good, but declining (e.g., €1.65 per €1)
🔴 High spend: Each extra euro barely adds profit (e.g., €0.34 per €1)
Even if your average performance looks good, continuing to invest where marginal ROAS or POAS is low or marginal CPA or CPC is high can waste budget.
Where to set marginal metrics in the automation form
Inside the Automation form, there is an option to select the Optimisation type of the Automation. Here, you can select Marginal ROAS/CPA/CPC/POAS (depending on the selected goal metric).
How our automation uses Marginal Metrics
You can now set a Marginal ROAS, Marginal CPA, Marginal CPC or Marginal POAS threshold in your automation. The system will:
Increase spend on campaigns where the next euro is expected to outperform your threshold
Reduce spend where performance falls below your target
Reallocate budget to higher-performing opportunities
Why It Works
Prevents overspending in low-performing campaigns
Helps scale up high-performing campaigns faster
Maximises the efficiency of every euro spent
Setting a Marginal ROAS, CPA, CPC or POAS Threshold
When you set a threshold (e.g. Marginal ROAS = 3.0, Marginal CPA = €10, Marginal CPC = €0.50, Marginal POAS = 2.0), remember:
Your average ROAS and POAS will typically end up higher, and your average CPA and CPC will be lower.
The system stops investing before the exact threshold is hit.
Early, efficient spend skews results favourably.
This gap between marginal and average is expected and beneficial.
Best Practices for Getting Started
Start conservatively
We suggest beginning with a lower threshold (e.g. 1.0 to 2.0 ROAS, 1.0 to 2.0 POAS, a slightly above average CPA or CPC) to reduce risk, a high threshold may lead to a decrease in budget, as the Automation will recommend to decrease spending.Monitor performance closely
Watch which campaigns are scaled up or down and how results evolve.Adjust gradually
You can raise the threshold daily based on your confidence and performance data.Allow for conversion lag
Give the system time to learn and adapt to your unique campaign dynamics.Disable 'Sync Total Daily Budget with Ad Managers'
How It Interacts with Other Rules
Marginal metrics automations work in harmony with your other existing settings:
Maximum daily budgets remain intact.
Other automation rules can still run, but we recommend avoiding heavy manual interference at the campaign or ad set level.
Overall ROAS/ CPA/ CPC/POAS monitoring continues to guide your broader strategy.
Summary
Marginal metrics bring a smarter, more agile way to allocate your ad budget. Instead of just reviewing past performance, you can now optimise based on future potential. By focusing on where your next euro will deliver the best return, lowest cost or highest profit, you avoid waste and accelerate growth in your most efficient campaigns.
Remember: Even a great-performing campaign might not deserve more budget if its marginal efficiency has dropped.
Need help getting started or choosing the right threshold? Reach out to your Customer Success Manager or support@billygrace.com.