The iPad/iPhone cannot be synced because there is not enough free space, but lots of space available

I was having a problem recently where I was attempting to sync my iPad in iTunes and was getting the "iPad cannot be synced because there is not enough free space" message. The thing is, I had a ton of free space on my iPad. I searched the web, and most solutions were basically, restore you device. Not a great solution. Plus, no one seemed to know the cause.

Well, I found what was causing the problem, and a solution. Sometimes the music on your device is not recognized as music in your library in iTunes. This can also happen if you have restored from a back up, or your last sync was not complete... or for any other reason under the sun. So when you try to sync, iTunes sees the music on your device as new music, and wants to sync it to iTunes, and then everything back to your device.

For example, if your library was 17 GB, iTunes would see this 17 GB as used space on you device as new music (music not in your iTunes library). So when you go to sync your device, the 17 GB in you library is added to the 17 GB of what iTunes thinks is new music on your device... so, 34 GB in total. If you only have a 32 GB device, you will get the message "not enough space to sync...". Luckily, the fix is really easy. In iTunes, click on your device and go to music. Deselect everything, essentially removing all music from your device, and sync. Then, select your entire library and sync again. Voila!... no more error message.

Hope this helps anyone having this issue.

Cheers!