How many pictures will a memory card hold?

The answer depends on the level of compression and the resolution (megapixels) of the camera. A way to estimate how many RAW (unprocessed and uncompressed) photos will fit on a memory card is to divide the gigabytes of the card by three times the pixels of the camera . For example: a 1GB memory card is about 1 billion bytes. A 5MP camera is 5 million pixels. Each pixel on a color RAW image file uses three bytes, so divide 1 billion by 15 million and you get about 67 photos. If you shoot in JPEG format, you will normally get roughly twice as many photos than this estimate because the camera compresses the photo information to save memory space. (It is impossible to say exactly how many more, as it depends on the color values in each picture and the level of compression.)