# Calculate the size of the system after enhancement

The functional size of a system may change as a result of the enhancement. The size after enhancement can be calculated by analysing the whole application anew or by taking account of the changes from the original FPA analysis. Steps to take are:

1. Calculate the function point size of the application prior to the change (FP BASE ) using the standard FPA method.
2. Identify the transactional and data functions deleted from the existing application and determine their function point size (Σ FP DELETED ).
3. Determine the transactional and data functions changed. Calculate the number of function points these represent before and after the enhancement (Σ FP AFTER and Σ FP BEFORE ), using the standard FPA method.
4. Determine the transactional and data functions added to the system and calculate how many function points these represent (Σ FP ADDED ).
5. Calculate the size of the system after enhancement (FP NEW ).

FP NEW = FP BASE + (Σ FP ADDED ) + (Σ FP AFTER-CHANGE - Σ FP BEFORE-CHANGE ) - (Σ FP DELETED )

Note: the Impact Factor does not play when determining the size of the system after enhancement.