In general, storage capacity depends on which image size and quality you have selected.
For your information, here is the number of images recordable in a 64MB SD Memory Card in the respective image size and quality. Since the image size may vary depending on scenes and subjects, these are approximate values only.
Economy: 125/242/352/968
Standard:63/125/193/645
Fine: 32/64/99/352
Super Fine: 5/10/17/65
(Pixel Size: 2272x1704/1600x1200/1280x960/640x480)
Movie: 2 min. 56 sec.
Audio Recording: 2 hr. 9 min. 9 sec.