Conversion rate
Conversion rate is the proportion of visitors who complete a desired action, such as making a purchase or submitting an enquiry.
In full
Conversion rate is the number of visitors completing a defined goal divided by total visitors, expressed as a percentage. The goal varies by business: a purchase for a retailer, an enquiry form for a service business, a booking for a clinic, a download for a software company. Rates differ enormously by industry, traffic source, and device, which makes cross-industry benchmarks close to useless. The meaningful comparison is your own rate over time, and the meaningful analysis is where in the funnel people leave rather than the headline number.
Why it matters
Improving conversion rate compounds against all existing traffic, which usually makes it cheaper than acquiring more visitors to the same underperforming page.
A common misconception
That a low conversion rate means the design is wrong. It frequently means the traffic is wrong, arriving with intent the page was never built to serve.