Method and assumptions
Use metrics from the same campaign, attribution window and reporting period. Mixing platform-attributed conversions with another revenue source makes the ratios misleading.
CTR = clicks / impressions. CPC = spend / clicks. CPM = spend / impressions × 1,000. CPA = spend / conversions.
Worked scenario
Use impressions, clicks, spend and conversions from one campaign and reporting window. Read CTR, CPC, CPM and CPA together: a CPA increase can come from higher CPC, lower conversion rate or both. Add revenue and contribution separately before treating delivery efficiency as business profitability.
How to interpret the result
These metrics form a diagnostic chain. CPM reflects the cost to access impressions, CTR converts impressions to visits, CPC combines the two, and conversion rate turns visits into the chosen action. CPA is meaningful only when a conversion is consistently defined and valuable enough to support the cost.
Input reference
- Currency
- Example default: USD
- Impressions
- Example default: 100000
- Clicks
- Example default: 2500
- Advertising spend
- Example default: 2000
- Conversions
- Example default: 100
- Attributed revenue
- Example default: 6000
Common mistakes
- Mixing platform clicks with analytics sessions without reconciliation.
- Changing the conversion definition between periods.
- Judging profitability from CPC or CTR alone.
Before using the result
- Lock campaign, date and attribution scope.
- Investigate the metric where the funnel first deteriorates.
- Connect CPA to contribution per acquired customer.
Questions to check before deciding
Can I compare campaigns from different attribution windows?
Not reliably. Standardize the attribution window before comparing efficiency.
Why is platform ROAS different from store ROAS?
Attribution rules, view-through conversions, time zones and refund treatment can differ.
Independent calculator. Not affiliated with or endorsed by the platforms mentioned.