How Many people in the President's Cabinet?

By tradition the cabinet of made up of the department department secretaries of which there are currently 15.

One might include the President's chief of staff as well and maybe other staff members such as the UN ambassador and the head of OMB. Obama included the vice-president in the official photo of the cabinet.

(FYI, the heads of 15 executive departments are the Secretaries of Agriculture, Commerce, Defense, Education, Energy, Health and Human Services, Homeland Security, Housing and Urban Development, Interior, Labor, State, Transportation, Treasury, and Veterans Affairs, as well as the Attorney General(head of Justice)