Custom Metric
AnalyticsAlso: Custom Dimension · User-Defined Metric
Quick definition
A custom metric is a measurement you define yourself inside an analytics platform, beyond the standard ones the platform provides by default. In Google Analytics 4 (GA4), custom metrics let you track business-specific signals like quiz completions, document downloads, or video watch depth that GA4 does not measure out of the box.
How it varies across Australia
Most Australian businesses use fewer custom metrics than they should, and those that do define them often leave them unmaintained as the product changes. The gap between what a business says it tracks and what its analytics actually measures tends to widen over time without deliberate governance.
See data and tracking maturity across Australian industries →What it actually means
Every analytics platform ships with a set of default measurements: sessions, pageviews, bounce rate, conversions. These are useful but generic. They were designed to work for every business, which means they were designed to fit none of them perfectly.
A custom metric is how you close that gap. It lets you track the specific actions and values that matter to your business model. A SaaS business might create a custom metric for the number of features a user activates before converting. An ecommerce brand might track the ratio of product page views to add-to-cart events. A publisher might measure scroll depth by article category.
In Google Analytics 4 (GA4), custom metrics are built on top of custom events. You fire an event when a meaningful thing happens, attach a numeric value to it, and register that value as a custom metric in the GA4 admin. From there it appears in reports, can feed attribution models, and can flow into Looker Studio or BigQuery for deeper analysis.
The distinction between a custom metric and a custom dimension matters too. Dimensions describe attributes (what type of user, what product category, what plan). Metrics count or measure things (how many times, how far, how much). Mixing them up in GA4 is one of the more common setup errors we see when auditing tracking configurations.
Custom metrics work alongside standard metrics like conversion rate, session duration and engagement rate. The goal is to complement the defaults, not replace them.
If you're only measuring what the platform decided to measure, you're optimising for the platform's definition of success, not yours.
How it shows up
Custom metrics show up wherever standard platform metrics appear: exploration reports in GA4, dashboard cards in Looker Studio, segment filters in ad platforms. In GA4 specifically, they appear in the Explore section once registered, and can be used as conditions in audience definitions.
The most useful custom metrics usually live at the intersection of product behaviour and revenue. A metric that counts the number of times a user reaches a meaningful milestone (pricing page view after feature use, document sent, third login in a week) gives marketing a signal the platform can never provide by default. That signal feeds smarter attribution, better audience segmentation, and more honest conversion tracking.
The Australian context
Australian businesses building on GA4 after the Universal Analytics (UA) sunset often discover that their previously tracked custom metrics did not migrate cleanly. UA custom dimensions used a numbered slot system. GA4 uses a named parameter system. The mapping is not automatic, and many businesses lost months of historical context during the migration.
For Australian businesses with privacy obligations under the Privacy Act, custom metrics also require careful review. If the numeric value attached to a custom metric can be used to re-identify an individual, that creates a compliance risk. Aggregated metrics are fine. User-level custom metrics need a closer look before they enter any downstream export.
Where people get this wrong
Related terms
Common questions
How many custom metrics can I create in GA4?
GA4's free tier allows up to 50 custom metrics per property. GA4 360 raises that limit significantly. In practice, most businesses need far fewer than 50. If you're approaching the limit, that's usually a sign of metric sprawl, not genuine measurement need.
What's the difference between a custom metric and a conversion in GA4?
A conversion is a specific event you've marked as a key business action. GA4 counts and attributes it. A custom metric is a numeric value attached to any event, not necessarily a conversion. You can have a custom metric on an event that isn't a conversion, and a conversion that has no custom metric attached.
Do custom metrics work in Google Ads audiences?
Yes, if your GA4 property is linked to Google Ads and you're using GA4-based audiences. Custom metric values can feed audience conditions, which means you can build audiences around business-specific thresholds rather than just standard platform signals.
Can I apply custom metrics retrospectively in GA4?
No. GA4 only applies custom metric definitions to data collected after the metric is registered. Historical data before registration does not get backfilled. This is different from Universal Analytics, and it means the sooner you define your metrics the more data you have to work with.
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About New Rebellion
New Rebellion is a marketing intelligence consultancy. We build tools, score Australian businesses on how their marketing actually performs, and publish Debrief every day. This dictionary is part of how we work in the open.
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