Analysis
Calculated metric
Also called derived metric.
Calculated metric is a metric defined as a formula over other metrics, such as revenue divided by sessions. The tool computes it on demand rather than storing it.
How it is measured
A calculated metric needs a clear numerator, denominator, and rule for empty rows. Its value depends on how the inputs are filtered, so the same formula can differ between two reports.
Check it by recomputing one row by hand from the raw inputs. Then compare the total row, because averaging rates across rows is a different calculation from dividing the totals.
Worked example
A pottery studio defines 'workshop signup yield' as signups divided by class-page views. In the data, Tuesday has 14 signups on 560 views and Saturday has 9 on 150 views.
Averaging the two day rates gives 4.3 percent. Dividing the totals gives 23 on 710, or 3.2 percent. The studio fixes the report to divide totals and writes the formula into the metric description.
How it differs
A calculated metric is built from other numbers. A plain metric is something the collector counts directly. The first inherits every flaw of its inputs.
Common errors
Averaging row rates instead of dividing totals. Dividing by a metric that can be zero. Mixing sessions in the top and users in the bottom. Hiding the formula. Editing it after reports have been shared.
In practice
Keep a short list of each formula and its owner. Name the metric for what it measures. When you change a formula, create a new name and let the old one stand.