Conversion Rate

Conversion rate is the percentage of sessions or users who completed a desired action (a conversion) out of the total number of sessions or users. In GA4, it is calculated as key events per session or key events per user.

Category: Analytics (also: Marketing)

Author: Atomic Glue Analytics Team

## Definition

Conversion rate measures how often users complete a desired goal on your website or app. The goal can be any meaningful action: a purchase, a signup, a form submission, a download, or a key engagement like a video view. In GA4, what used to be called 'conversions' are now 'key events,' and conversion rate is reported as key event rate (key events per session) or users who triggered a key event (as a percentage of total users). The formula is straightforward: (Number of conversions / Total sessions or users) x 100. The nuance lies in what counts as a conversion, how you attribute it, and whether you measure it per session or per user. A 5% conversion rate means 5 out of every 100 sessions (or users) resulted in the desired action.

## GA4 key events (formerly conversions)

In GA4, any event can be marked as a 'key event.' This replaces the UA concept of goals. When you mark an event as a key event, GA4 surfaces it in the key events report and includes it in conversion rate calculations. You can mark up to 30 unique key events per property (standard) or more on 360. You can also assign monetary values to key events to track total conversion value.

## Session-based vs user-based conversion rate

GA4 calculates both. Session key event rate: total key events / total sessions. User key event rate: total users who triggered a key event / total users. Session-based rates are generally higher because one user can have multiple sessions. User-based rates reflect the actual portion of your audience that converted. Choose based on what you want to measure: campaign effectiveness (session) or audience penetration (user).

## Factors affecting conversion rate

Traffic source quality matters. Paid traffic often converts differently than organic. Device type, landing page experience, page load speed, checkout friction, and trust signals (reviews, security badges) all influence conversion rate. Seasonality, promotions, and market conditions also play a role. A 'good' conversion rate varies wildly by industry: ecommerce averages 2-5%, B2B SaaS lead-gen forms average 5-15%, and high-intent landing pages can see 20-40%.

## Note

Misconception: a 'good' conversion rate is a universal number. It is not. Industry benchmarks are directional at best. Your conversion rate depends on your business model, traffic mix, pricing, and funnel complexity. Also: marking too many events as key events dilutes the metric. Pick 3-5 events that directly map to business outcomes, not every micro-interaction.

## In code

// Marking an event as a key event via GA4 configuration in GTM
// In the GA4 Event Configuration tag, toggle "Mark as key event"
// Or via gtag.js:
gtag('event', 'purchase', {
  value: 49.99,
  currency: 'USD',
  transaction_id: 'TXN_78901'
  // Also define this event parameter as a key event in GA4 admin
});

## Common questions

Q: What is the difference between a goal (UA) and a key event (GA4)?

A: In UA, goals were configured in the admin panel and had types (destination, duration, pages/session, event). In GA4, any event can be marked as a key event with a simple toggle. There are no goal types. It is simpler but less flexible for certain use cases like duration-based goals.

Q: Can I have multiple conversion rates?

A: Yes. Each key event has its own rate. You should track macro conversions (purchases, signups) and micro conversions (email clicks, video views, add to cart) separately.

Q: Does GA4 count each conversion event or the first one per session?

A: It depends on your key event counting method. You can set each key event to count 'once per session' or 'every time' it fires. This is configured per key event in the GA4 admin.

## Key takeaways

• Conversion rate = conversions / total sessions or users
• GA4 uses 'key events' instead of UA's 'goals'
• Up to 30 key events per standard GA4 property
• Choose session-based or user-based rates depending on your analysis
• Benchmarks vary by industry; focus on your own trend and improvement

## Related entries

• [Google Analytics 4 (GA4)](atomicglue.co/glossary/google-analytics-4-ga4)
• [KPI](atomicglue.co/glossary/kpi)
• [Attribution Modeling (First-Click, Last-Click, Multi-Touch, Data-Driven)](atomicglue.co/glossary/attribution-modeling)
• [ROAS](atomicglue.co/glossary/roas)

Last updated July 2026. Permalink: atomicglue.co/glossary/conversion-rate