Relativity has a mass operation application, "Set Long Text Field Size" which you can use to calculate the size of long text field. A decimal field must be set up to hold the value that this mass op generates.

The text size will be listed in kilobytes - KB. This mass operation works like others - you need to check off the items you want to process, or check all items in a set. It will be possible to edit the documents in this set for the text field size even if you only have read only permissions to the documents.

A new form will appear. On this form will be a drop down menu of the existing long text fields. Another drop down menu will give you access to all decimal fields that have been set up.