How to calculate the area of elbow, tee, reducer and head?

The area of elbow, tee, reducer, head and so on, if it is used for calculation of project quantity, it can be calculated with its center line of "extended meter" as straight pipe, and if it is required for its exact data, it should be unfolded and calculated. This is indeed some trouble, but with the software "AutoPOL for Windows" to expand, a pipe can be as long as 1 minute, after the expansion of the export to AutoCAD, fill in the expansion of the area can be queried to its area.