CRO (Conversion Rate Optimization)
CRO (conversion rate optimization) is the systematic increase of the share of users who take a desired action on a website. That action can be a purchase, a form submission, a newsletter sign-up or a file download. CRO does not increase traffic; it makes better use of the traffic the site already has. It is based on data analysis, research into user behaviour and testing changes, e.g. in A/B tests.
How is the conversion rate calculated?
The conversion rate is the number of conversions divided by the number of sessions or users, multiplied by 100%.
CR = number of conversions / number of sessions or users × 100%
Example: a shop had 20,000 sessions and 400 orders in a month. Its conversion rate is therefore 400 / 20,000 × 100% = 2%. If CRO raises it to 2.5% with the same traffic, the shop will get 500 orders, that is 100 more.
In Google Analytics 4, conversions are called key events. The tool reports two metrics:
| Metric in GA4 | What it measures |
|---|---|
| session key event rate | the share of sessions in which a key event occurred |
| user key event rate | the share of users who triggered a key event |
The result therefore depends on what you take as the denominator. When comparing, always use the same calculation method.
What does the CRO process look like?
CRO is a process repeated in a cycle: research, hypothesis, test, analysis and rollout. Every change is checked against data before it goes live permanently.
- Data analysis. In an analytics tool you look for the points where users abandon the path, e.g. the cart or a form.
- Behaviour research. Heatmaps, session recordings, surveys and user tests show why people give up.
- Hypothesis. The team writes down what to change, for whom and what effect it expects.
- Test. The change is checked in an A/B test or a multivariate test on part of the traffic.
- Analysis and rollout. When the result is statistically significant, the winning version goes to all users.
| Method | What it is for |
|---|---|
| A/B test | comparing two versions of a page on split traffic |
| Multivariate test | checking several changes at once and their combinations |
| Heatmaps | showing where users click and how far they scroll |
| Session recordings | watching the actual path a user takes through the site |
| Surveys and interviews | learning why people abandon a purchase |
CRO changes concern content, layout, forms, the purchase path and page speed. Speed can be checked in PageSpeed Insights, and events for analysis can be configured in Google Tag Manager. On mature sites, removing unnecessary elements often brings more than adding new ones.
How does CRO differ from SEO?
SEO increases the number of people who reach the site from a search engine. CRO increases the share of those people who take the desired action.
| Feature | SEO | CRO |
|---|---|---|
| Goal | more traffic from organic results | more conversions from current traffic |
| Main metrics | rankings, impressions, clicks | conversion rate, order value |
| Area of work | content, links, site technology | layout, sales copy, forms, purchase path |
| Verification method | monitoring rankings and traffic | A/B and multivariate tests |
The two approaches complement each other. A fast, clear site helps both SEO and conversion. A CRO specialist, however, does not look only at the conversion rate. They choose metrics that best match business goals, e.g. revenue per user or ROI.
Frequently asked questions
Q.What is CRO?
CRO, or conversion rate optimization, means optimizing the conversion rate. It involves increasing the share of users who take a desired action on a site, e.g. buy or submit a form. It is based on data analysis, research into user behaviour and testing changes. It does not increase traffic; it makes better use of it.
Q.How do you calculate the conversion rate?
The conversion rate is the number of conversions divided by the number of sessions or users, multiplied by 100%. For example, 400 orders from 20,000 sessions gives 2%. In Google Analytics 4, conversions are called key events. When comparing, always calculate the same way, on sessions or on users.
Q.What is an A/B test in CRO?
An A/B test compares two versions of a page that different groups of users see at the same time. Version A is usually the current page, and version B contains one change. After collecting enough data, you check which version produced more conversions. This limits the risk of bad changes.
Q.Is CRO the same as SEO?
No. SEO increases the number of visitors from a search engine, while CRO increases the share of visitors who take the desired action. SEO is measured by rankings and clicks, CRO by conversion rate and revenue. The two complement each other, because more traffic gives more data for tests.
Q.What sources is this description based on?
The scope of CRO, the role of A/B and multivariate tests and the choice of metrics are described in the Analytics Toolkit glossary. The key event metrics in Google Analytics 4 and how they are calculated are described by MeasureU. The example with 20,000 sessions and 400 orders is an illustrative calculation, not data from a specific shop.
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