Tom, welcome to the forum. Your answer is in chapter 9, take notice of note 9 to the Tables
(9)A multiconductor cable of two or more conductors shall be treated as a single conductor for calculating percentage conduit fill area. For cables that have elliptical cross sections, the cross-sectional area calculation shall be based on using the major diameter of the ellipse as a circle diameter.
After determining the dimension of the cable, go to the appropriate conduit table and do the math.
As an aside, the chapter 3 xxx.22 conduit and tubing sections of the 2005 NEC clears up the question of whether cable assemblies are allowed to be installed in complete conduit systems.
Cables shall be permitted to be installed where such use is not prohibited by the respective cable articles. The number of cables shall not exceed the allowable percentage fill specified in Table 1, Chapter 9.
[This message has been edited by Roger (edited 03-16-2006).]