Check the sys.columns
system catalog view:
SELECT *
FROM sys.columns
WHERE is_computed = 1
This gives you all computed columns in this database.
If you want those for just a single table, use this query:
SELECT *
FROM sys.columns
WHERE is_computed = 1
AND object_id = OBJECT_ID('YourTableName')
This works on SQL Server 2005 and up.
UPDATE: There’s even a sys.computed_columns
system catalog view which also contains the definition (expression) of the computed column – just in case that might be needed some time.
SELECT *
FROM sys.computed_columns
WHERE object_id = OBJECT_ID('YourTableName')