Custom Metric

A custom metric registers a numeric parameter you collect so GA4 can count, sum, or average it in reports. Where a standard metric is a built-in number like sessions or conversions, a custom metric lets you measure quantities specific to your business — a lead score, an item quantity, a video percentage watched.

Why it matters

GA4 measures the things Google decided everyone needs. But plenty of businesses generate their own numbers worth tracking. A custom metric is how you bring those into reporting so they can sit alongside the standard figures and be totalled or averaged like any other number.

A concrete example

Suppose your contact form sends a parameter called quote_value — the rough budget a prospect enters. Register it as a custom metric, and GA4 can sum the total quoted value of leads per week or average it by traffic source. Now you can see not just how many leads a channel brings, but how valuable they tend to be — a far better signal than raw lead count.

The common misreading

The classic mistake is trying to register a text value as a custom metric. Metrics must be numbers; if you want to group by a label like author or topic, you need a custom dimension instead. The second trap is the retroactivity assumption — like dimensions, custom metrics only populate from the date you register them, so historical events stay empty.