Salesforce Tips: Roll-up summary with formula fields

Can Roll-up summary field works with Formula field? The answer is Yes and No.

Yes if the Formula field is not referring to a field from foreign object. Let me give you an example:

Project (Parent object)

• Project Name (Text 50)
• Due Date (Date)
• Total Cost (Roll-up Summary : Sum of all child Project Items Calculated Cost)

Project Item (Child Object)

• Project Item Name (Text 50)
• Item Quantity (Number 18, 0)
• Item Price (Currency 16, 2)
• Calculated Cost (Formula = Item Quantity * Item Price)

No, if the Formula field is referring to another field in a different object. Let me use the same example:

Project (Parent object) (Same as above)
Project Item (Child Object)

• Project Item Name (Text 50)
• Item Quantity (Number 18, 0)
• Related Item (Lookup : Product)
• Calculated Cost (Formula = Item Quantity * Product.Price)