Your optimal bitrate will depend on your encoder and the features you have chosen to enable.
The following rough calculation provides you with a good baseline Kbps:
(FRAME_HEIGHT * FRAME_WIDTH * FRAME_RATE) / MOTION_FACTOR / 1024 = BASELINE Kbps
where MOTION_FACTOR is:
- 7 for high-motion, high screen-change clips
- 15 for standard clips
- 20 for low-motion (talking head) clips
Note: This is just a suggested algorithm to get you started; your mileage might vary. Keep in mind that clips almost always tend to be higher motion than you originally anticipate. The outcome is also dependent on the features you enable.