Conversion rate is only meaningful when its denominator is named.
Sessions
Session conversion rate measures the share of visits that convert. It is useful for website experience analysis but allows one person to enter the denominator several times.
Users
User conversion rate asks what share of identified users converted during a period. Identity limitations, cookie consent and cross-device behavior affect the count.
Clicks and leads
Ad click-to-conversion rate evaluates post-click efficiency. Lead-to-sale rate evaluates sales qualification and closing. They should not be compared with a sitewide session conversion rate.
Keep event definitions, identity rules and time windows unchanged when measuring trends.
Sources
This guide is educational and does not provide financial, accounting, tax or legal advice.