GA4 conversion rate tells you what proportion of visits result in a purchase, but the number changes depending on whether you measure sessions or users. For day-to-day ecommerce reporting, session conversion rate is usually the clearest measure because it answers a simple question: out of all the shopping sessions, how many produced an order?

Before calculating anything, confirm that the purchase event is working, revenue is reaching GA4 and internal traffic is excluded. A clean formula cannot repair broken tracking.

Measure conversion rate in a standard report

1. Open the right property and date range. In GA4, select the property for the store, then set the reporting dates in the top-right corner. Turn on comparison with the previous period or previous year if you need context, but keep both periods the same length.
2. Go to Reports, then Acquisition, then Traffic acquisition. This report is session based, so it is the right place to compare ecommerce conversion by channel, source or campaign without mixing user and session measures.
3. Change the main dimension if needed. Use Session default channel group for a broad view, or change it to Session source / medium when you need to separate Google organic, Google paid, Meta referral traffic and email traffic.
4. Add the Sessions, Ecommerce purchases and Session key event rate columns. If purchase is marked as a key event, filter the report to purchase so the rate is not inflated by other key events such as form submissions or newsletter sign-ups.
5. Calculate the rate manually as a check. Divide ecommerce purchases by sessions, then multiply by 100. If the store recorded 120 purchases from 4,000 sessions, the session conversion rate is 3%. This should be close to GA4's session key event rate when purchase is the only event included.
6. Check by device and channel. Add a secondary dimension such as Device category, or build the same view in Explore. A blended site rate can hide a serious mobile problem or a poor-quality campaign.

Check the number before reporting it

Compare GA4 purchases with Shopify orders for the same dates, allowing for timezone differences, refunds and orders created outside the online store. The numbers will rarely match perfectly, but a large or sudden gap needs investigating before the rate is used in a report.

Do not divide total users by orders and call it session conversion rate. User conversion and session conversion answer different questions, so label the measure clearly and use the same definition every week. Also avoid judging a small channel from a handful of sessions, because one sale can make the percentage look far more meaningful than it is.