Short definition
Conversion rate is the percentage of website visitors who complete a defined goal, such as filling out a form, calling, or making a purchase.
In depth
Conversion rate is the most important downstream metric on any service-business website. Calculate it as conversions divided by visitors over a given period. For lead-gen service sites, healthy benchmarks are 2–5% on cold traffic and 8–15% on branded or returning visitors. Track multiple conversion types — primary (proposal request), secondary (newsletter, audit download), and micro (scroll depth, video completion) — so you understand the funnel and can optimize each step.
Example
A roofer's homepage gets 1,200 visits a month. 36 fill the quote form. Conversion rate = 3.0%. After CRO work it rises to 4.5% — 18 more leads on the same traffic.