Use the following formula to calculating the size for enhancement projects.

**EFP = [(ADD + CHGA + CFP) * VAFA] + (DEL* VAFB)**

Where:

- EFP is the enhancement project function point count.
- ADD is the unadjusted function point count of those functions that were added by the enhancement project.
- CHGA is the unadjusted function point count of those functions that were modified by the enhancement project. This number reflects the functions after the modifications.
- CFP is the function point count added by the conversion.
- VAFA is the value adjustment factor of the application after the enhancement project.
- DEL is the unadjusted function point count of those functions that were deleted by the enhancement project. It is important to consider the absolute value of the DEL not the negative value.
- VAFB is the value adjustment factor of the application before the enhancement project.

In practice:

EFP = [(ADD + CHGA + CFP) * VAFA] + (DEL* VAFB)

In practice VAFA = VAFB = VAF, so the equation becomes

EFP = (ADD + CHGA + CFP+ DEL)* VAF)

Also normally CFP = 0, so the equation simplifies further

EFP = ((ADD + CHGA + DEL)* VAF)

To examine the equation in detail letâ€™s assume that VAFA = VAFB = 1 and CFP = 0. Hence EFP = (ADD + CHGA + DEL). That is, the size of an enhancement project is a summation of all added functionality, changed functionality and any deleted functionality.

In theory and in practice, each piece of the formula must be adjusted by the appropriate Value Adjustment factor. Assume now that VAFA <> VAFB. The added and changed after is adjusted by the VAFA, but the deleted is adjusted by the VAFB. Additionally, if CFP <> 0 then it should be adjusted by VAFA.