How does acalculated column work in Sharepoint? When a calculated column is added to the list, at the next moment it will update the list items. How does this happen?
Computed columns in SharePoint 2010 are similar to formulas in an Excel spreadsheet. Their result is achieved by writing a formula that uses the values of other columns (their names). There are all kinds of formulas for performing calculations, as indicated in Calculated Field Formulas -msdn, with an example and a possible result. You can also check out the two links below that show the steps to reach the calculated column:
Hope this makes things clearer.
Short answer: it updates the value when the item is saved or when the calculation changes in the field setting
read this very interesting post. The discussion in the comments section is very interesting.
The calculated fields are saved in the database and updated when the input is saved.