While editing a report, in 'Measure' drop-down, you'll see the list of calculated metrics (metrics which are valid with chosen dimension.)
Below GIF shows the CTR (Clicks/Impressions) in AdWords report.
Follow the steps below to create a report using calculated metrics.
Step 1: Go to Reports
Step 2: Create a report or edit an existing report
Step 3: Drag and drop a widget on to the report
Step 4: Click on + Add Metric button to create a new metric
Step 5: Find the created metric in Measure drop-down, under Calculated Metrics group
Step 6: Send this report to your clients😃
Have questions about getting started with Calculated Metrics? Feel free to reach out to us at firstname.lastname@example.org