> For the complete documentation index, see [llms.txt](https://helpcenter.channable.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://helpcenter.channable.com/manage-improve-product-data/rules-bulk-edit-and-enrich/how-to-use-actions-then-in-rules/rule-action-calculate-list-length.md).
# Rule action: Calculate list length
Used for: calculating how many elements a list has.
Used in: “THEN”-statements and “ELSE”-statements.
## Calculate list length
The "calculate list length" rule determines the number of elements in a list. This is particularly useful when you have all the available sizes of a product in a list and need to calculate the total number of sizes available.
For instance, if you have a list of sizes for a product, you can use this rule to determine how many sizes are available. The example rule in the screenshot below illustrates how this works for a specific product:
In the screenshot below, you can see how this rule would work for a specific product:
### Calculate List Length (Unique Elements)
This is an extension of the “calculate list length” rule. It allows the user to count only unique elements in a list. This can be useful for ensuring that duplicate sizes are not counted multiple times.
For instance, if you have a list of sizes for a product, you can use this extension of the rule to determine how many unique sizes are available. In the screenshot below, you can see how this rule would work for a specific product:
In the screenshot below, you can see how counting only unique values in a rule works for a specific product:
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