A metric is a number that measures something: how many, how much, how often or what proportion. In analytics, sessions, users, key events, revenue and engagement rate are all metrics. They are always quantities, which is what separates them from dimensions, the descriptive labels such as page, city or traffic source that you break metrics down by.
How metrics work
Every analytics report is a table of dimensions and metrics. In “sessions by city”, city is the dimension and sessions is the metric. Change the dimension to landing page and the same metric is split a different way.
Metrics come in a few kinds, and knowing which you are looking at prevents wrong conclusions:
- Counts Such as sessions or form submissions. They add up across rows.
- Sums Such as revenue or items purchased. They also add up.
- Ratios and averages Such as conversion rate, engagement rate or average order value. These do not add up; you cannot total two pages’ conversion rates.
- Unique counts Such as users. A person who visits three pages is one user on each page row but still one user overall, so row totals can exceed the true figure.
Metrics also have a scope in GA4. Some are measured per event, some per session and some per user, and mixing scopes in one report can produce numbers that look wrong but are behaving exactly as designed. Where GA4’s built-in metrics do not cover what you need, you can register a custom metric from an event parameter, such as a quote value sent with each enquiry.
Why it matters
A UK business owner looking at a monthly report has limited time. If the report leads with page views, impressions and followers, it can look healthy while enquiries fall. The metrics you choose to watch decide what the business pays attention to, and paid platforms such as Google Ads optimise towards whatever metric you give them as a conversion.
The useful distinction is between metrics that describe activity and metrics that tie to money. An actionable metric tells you what to change. A vanity metric makes you feel good without telling you anything you can act on. A short list of the former, often called KPIs, is worth more than a dashboard of fifty numbers.
Common mistakes
- Averaging averages: adding several conversion rates and dividing, instead of recalculating from the underlying counts.
- Comparing metrics with different definitions across tools, such as a Meta “result” and a GA4 key event, and expecting them to match.
- Reading a ratio without its volume. A 20% conversion rate on ten visits means little.
- Choosing metrics because the tool shows them by default rather than because they answer a business question.
- Changing a metric’s definition partway through the year without noting it, so trends break.
How to act on it
Pick three to five metrics that connect directly to how the business earns money, such as qualified enquiries, cost per enquiry, revenue from organic search, or repeat purchase rate. Write a one-line definition of each, including which tool is the source of truth for it. Put those at the top of every report and treat everything else as supporting detail.
Then check each metric is measured correctly. A key event that fires twice, or revenue recorded including VAT on one platform and excluding it on another, will undermine any target set on top of it.
Agreeing the handful of metrics that matter, and the targets that sit on them, is a central part of the digital marketing strategy work I do before recommending where to spend.