It's not possible to answer this question because you haven't told us what make and model your camera is. To know how many pictures you will fit on your card, you have to know the resolution the pictures are being captured at. (How many mega-pixels you have.)
Also some cameras enable you to pick Normal or Best quality. This affects the amount of space each picture will take up.
Short answer is SD cards are quite cheap. Buy the best you can afford and you will probably be able to save several hundred photos on it.
Darren M, April 2009
