640,000 total points ~ 64mB file size
While sculpting in ZBrush your files can be as large as your system can handle. I usually sculpt at or around 4,000,000 points. To output your file for 3D printing however, you must decimate the model to 640,000 total points, or fewer, before you export to .stl format.
--- just some notes for me to reference in the future.