Conversion rate: the number, and what it hides
The share of visitors who completed the action you wanted.
Why conversion rate matters
It separates the ad's job from the page's job. If the ad is delivering clicks and the page is not converting them, more creative will not help.
What this looks like with real numbers
1,000 link clicks, 820 landing page views, 33 purchases. Over clicks that is 3.3%, over sessions 4.0%. The 180 people lost between the click and the page view are a speed problem, and no creative change will recover them.
What it does not tell you
Denominator matters. Conversions over clicks and conversions over sessions give different numbers, and traffic lost before the page loads sits in the gap between them.
The mistake people actually make
Reporting conversion rate over clicks while optimising page speed against sessions. The two move independently and it hides where the loss actually is.
Questions, answered.
How do you calculate conversion rate?
Conversions ÷ sessions (or clicks). The share of visitors who completed the action you wanted.
What goes wrong with conversion rate?
Reporting conversion rate over clicks while optimising page speed against sessions. The two move independently and it hides where the loss actually is.
What does conversion rate not tell me?
Denominator matters. Conversions over clicks and conversions over sessions give different numbers, and traffic lost before the page loads sits in the gap between them.
Change the creative, not the dashboard
The share of visitors who completed the action you wanted.