The 16 GB iPad is designed to hold 16 gigabytes of information, which is equivalent to 16,000 megabytes. Those megabytes can be made up with videos, songs or other information. For approximations, your iPad can hold up to about 4,000 songs depending on the length and how they are compressed and how many other items you have saved on your iPad.
You could fit about twenty hours of video on your iPad if you didn’t have anything else saved, such as images or songs, and also depending on the quality of the video and how it was compressed. Ultimately, a 16 GB iPad will hold 16 gigabytes of information and that information can be made up of a large amount of data including images, songs, videos and other file types. What you choose to save on your iPad and how much you will be able to fit within the 16 GB limit is up to you.
Resource: eHow