Calculating protein size - how to calculate the protein size when cloned in pet vector (Dec/21/2007 )

I would like to know theriotically how to calculate the protein size cloned in pET28A+ vector along with the His tag.

If my actual protein size is 15KDa, along with the His tag will it be 17-18 KDa.

Please help me

Joey

enter the whole protein sequence in this website and it will give you the mass.