It depends on several things.
Is this a CMOS or a CCD?
If CCD what speed of A/D converter are you using?
If CMOS what # taps and A/D speed on taps are you using?
Basically it's either
CCD - X res * y res = # reads / Mhz rate of A/D. So if you have 1,000,000 pixels in an array, and a 10Mhz A/D, you'll get 10FPS.
With CMOS you do the same but it's X res * y Res for # reads, then / # taps*tap speed. So if it's a 10 tap camera @ 1 Mhz each tap, it's 10Mhz readout rate.
This doesn't take into account vertical or parallel clock shifts, it assumes the readout is the limiting component, which it almost always is..