Definition
Organic cost per acquisition (organic CPA) measures the average cost of obtaining a conversion (customer, lead, sign-up) through organic search. It is calculated by dividing the total SEO budget (salaries, tools, link building, content, technical) by the number of conversions attributed to the organic channel. Organic CPA is generally much lower than paid traffic CPA (Google Ads) because SEO investment has a cumulative and lasting effect. Unlike paid ads where every click has a cost, organic traffic continues generating conversions even without additional active investment. Comparing organic CPA to paid CPA is a decisive argument for justifying SEO budgets.
Key Points
- Measures the real cost of acquiring a customer through SEO
- Typically 3 to 5 times lower than paid traffic CPA thanks to the cumulative effect
- Decreases over time as domain authority and content accumulate
Practical Examples
Organic vs. paid CPA comparison
A B2B site calculates an organic CPA of EUR 35 (SEO budget EUR 7,000 / 200 organic leads) vs. a Google Ads CPA of EUR 120, demonstrating the superior profitability of SEO.
CPA evolution over 12 months
At the start of an SEO campaign, organic CPA is EUR 150. After 12 months of continuous link building investment via LemmiLink, it drops to EUR 25 thanks to the cumulative effect of backlinks and content.
Frequently Asked Questions
Add up all monthly SEO costs (SEO team salaries, tools like Ahrefs/Semrush, LemmiLink link building budget, content creation, technical services) and divide by the number of organic conversions that month. Compare with CPA from your other channels.
In the long term, yes. But the first months of an SEO strategy can have a high organic CPA because results take time to materialize. It is generally after 6-12 months that organic CPA becomes significantly more advantageous than paid.
Go Further with LemmiLink
Discover how LemmiLink can help you put these SEO concepts into practice.
Last updated: 2026-02-07