How to Find out What Is Taking up Space on an iPhone
Apple's iPhone electronic device comes in versions with 8GB, 16GB and 32GB of storage space. Though this may seem like a lot, once you start syncing music and videos as well as applications that space can disappear quickly. If it seems like you should have more room left than you have, you can quickly find out what is taking up space on your iPhone using Apple's iTunes device management software.
Connect your iPhone to your computer. Allow a few seconds for your computer to recognize the iPhone.
Click on the arrow next to the "Devices" category heading on the left side of iTunes to expand it into a list of connected devices.
Click on the name of your iPhone. This will display the settings utility for your iPhone in the main iTunes program window. Your iTunes media library will not be visible during this time.
Look at the multicolored bar labeled "Capacity" on the bottom portion of the iPhone settings utility. The different colors present in the bar represent the different types of data that are on your iPhone. The key at the bottom explains what they are-- blue is audio, purple is video, green is applications, orange is "Other" and gray is free space. The numbers beneath the key represent exactly how much space, measured in gigabytes, that these elements are taking up.