CRO Glossary: Essential Conversion Optimisation Metrics Explained

Conversion Rate Optimisation (CRO) is driven by data, but that data is only useful when everyone interprets it the same way.

This CRO glossary explains the most important conversion optimisation metrics used in eCommerce, grouped by category and defined in plain language. Each term clarifies what the metric represents and how it helps teams understand performance across the customer journey.

If you're looking for exact formulas and step-by-step calculations, we've broken those down in our CRO Metrics and How to Calculate Them guide.

This article is designed as a reference guide, supporting marketers, product teams, and eCommerce leaders who want a shared understanding of CRO metrics before making optimisation decisions.

Note: Metrics are grouped by how they are typically used in CRO analysis, from high-level performance indicators to granular behavioural signals.

CRO Metrics at a Glance

The table below provides a high-level summary of the key CRO metrics covered in this glosssary, grouped by how they are typically used in optimisation analysis.

Primary Metrics (North Star Metrics)

These metrics reflect overall commercial performance and are typically used to guide high-level optimisation decisions.

Conversion Rate (CR)

The percentage of visitors who complete a purchase.

Conversion Rate indicates how effectively a site turns traffic into customers.

Revenue per Visitor (RPV)

The average value of each visit.

RPV combines conversion behaviour and order value to show how much revenue each visitor generates.

Customer Lifetime Value (LTV)

The total revenue expected from a customer over their lifetime.

LTV shifts CRO thinking from short-term wins to long-term value creation.

Gross Margin

The percentage of total sales revenue that the company retains after costs.

Gross Margin ensures optimisation efforts support profitability, not just revenue growth.

Secondary Metrics

Secondary metrics help explain why primary metrics move and where revenue growth is coming from.

Average Order Value (AOV)

The average amount spent by a customer per transaction.

Purchase Frequency

How often an average customer buys within a specific period.

Subscription Orders per Visitor

The frequency of recurring revenue generated per visitor.

Subscription Revenue per Visitor

The financial value of the subscription model per site visitor.

Repeat Purchase Rate

The percentage of customers who have made more than one purchase.

Subscription Rate

The percentage of users opting for recurring billing models.

Items per Order

The average number of products in a single transaction.

Average Product Revenue per Unit

[Avg Product Revenue / Unit]

The average selling price realised per unit sold.

Micro Metrics

Micro metrics focus on specific steps within the user journey and help identify friction or opportunity at a granular level.

Product Detail View Rate

Measures interest in specific products.

Product Listing Clickthrough Rate (CTR)

Effectiveness of category pages in driving users to products.

Add-to-Cart (ATC) Rate

Measures intent to buy and product or price appeal.

Checkout – Begin Rate

The transition from shopping to the buying phase.

Checkout Completion Rate

Efficiency of the final payment and shipping steps.

Search Usage Rate

Measures how proactive users are in finding products.

Search Conversion Rate

Effectiveness of site search results in driving sales.

No-Result Search Rate

Identifies gaps in inventory or search synonyms.

Acquisition Metrics

These metrics connect CRO performance with marketing efficiency.

Customer Acquisition Cost (CAC)

The cost to acquire one new customer.

Cost per Order (CPA)

Marketing cost spent to generate a single transaction.

ROAS – Return on Advertising Spend

Revenue generated for every unit spent on advertising.

Technical Metrics

Technical metrics assess site health and post-purchase quality.

Page Load Time

The average time it takes for a page to load.

Payment Success Rate

Measures the technical health of payment gateways.

Refund / Return Rate

Measures product satisfaction and post-purchase quality.

How to Use These Metrics in Practice

Understanding metrics in isolation is only the first step. The real value comes from knowing which metrics deserve attention first and how performance compares to realistic expectations.

If you want to sense-check how your store stacks up:

• Our CRO Benchmarks can help identify whether Conversion Rate, Average Order Value, or Repeat Purchase behaviour is the primary constraint.
  
  
• Reviewing eCommerce benchmarks, particularly Shopify benchmarks, provides useful context on what “good” looks like across your industry.
  
  
• A CRO Audit goes deeper, using behavioural data to explain why specific metrics are underperforming and where optimisation will have the biggest commercial impact.
  
  
• CRO Implementation is the ongoing optimisation phase, where insights from the audit are prioritised, implemented, and validated through structured testing and iteration over time.

This glossary gives you the language. Benchmarks and audits help you decide where to act.