How can I track Shopify conversion rate?

Although Shoify has a built-in analytics app, as you likely have found, it is very limited. If you want to gain full access to your site's analytics, with the ability to create multiple KPI tracking systems, there is no better resource than Google Analytics.

GA is easy to integrate into your Shopify store and will provide you with all the information that you need to scale your business.

That said, GA can be overwhelming to someone that's not used to it. If this is the case, or you simply want to focus on conversion rate, then apps such as BeProfit make the calculations and tracking of conversion and profit margins a lot simpler.