WooCommerce: Why don't the number of new customers match.
There can be a few different reasons for this.
Your store settings for what type of Customers or Orders are included in the report calculations are not the same.
i.e you may be excluding non-paying customers or certain order statuses on one platform but not the other.
Your date setting for filtering is set to Customer Joined / Registered and not First Ordered. (We recommend keeping this as First Ordered).
You have some customers who first ordered as Guest Customers at checkout, and then later on made orders as Registered Customers.
WooCommerce doesn't track guests (you can read about this here). So, if a customer's first order is placed where they checked out as a guest, WooCommerce doesn't see them as a new customer.
It is only when they place an order as a registered customer that they are logged as a new customer, which is essentially incorrect, as they have ordered before and are not new.
Example
Customer A places an order on December 20th 2024 and it is a guest checkout. They then placed a second order on January 11th 2025 but checked out as a logged-in registered customer.
WooCommerce will show them as being a New Customer in January 2025, Metorik however, will show them correctly being a new customer in December 2024.
This results in a difference in numbers between Metorik and WooCommerce. We'd recommend sticking to using Metorik for this stat, especially if you have allowed Guest checkouts on your site.