Upload & Sell: Off
The math is pretty simple:
8000 megabytes per card / 12 megabytes per photo = 666 photos per card
As noted by the above poster, an 8GB card has theoretical capacity of 8,192 MB (about 682 photos per card) but sometimes space has been allocated or is not otherwise writeable. So 8000 megabytes makes a decent estimate.
Actually it is the other way around.
A card that is advertised as 8gb actually has 8.000.000.000 bytes. For "simplicity", the manufacturers devide this number by 1000 three times, but in actual fact, they should be deviding by 1024.
8000000000 bytes / 1024 = 7812500 Kilo bytes
7812500 Kilo bytes / 1024 = 7629.39 Mega bytes
7629.39 Mega bytes / 1024 = 7.45 Giga bytes
Clear as mud I know, and my 'in head' calculation of 7.6gb is also wrong. A card advertised as 8gb will only give 7629.39mb, or 7.45gb of actual storage, minus of course any space that is used up by the cameras file system.