The Conversion Rate % in Webtrekk shows how many orders a user places per day. The formula for the Conversion Rate is "Qty Orders" (scope visit) / "Visitors, Daily Unique" * 100.
Google Analytics distinguishes between ecommerce conversion rate and conversion rate AdWords. Ecommerce conversion rate shows in percentage how many visits an ecommerce transaction included. Here, the formula is Conversions / Visits * 100. The conversion rate AdWords is calculated by dividing the number of conversions by the total number of ad clicks, which can be assigned to a conversion in the same time period. This formula is Conversions / Clicks * 100.