I use 120 MB of iCloud storage space for iCloud Backup of my iPad & iPhone. There is still 4.8 GB free from 5 GB, but I have a notification in iPad's backup window that I'm lacking space to back up to iCloud and would rather not buy more space to back up today.
This could easily be explained as the 120 MB of used data is likely for the data all the apps store in iCloud. Contacts, calendars, specific third party apps can have storage in iCloud. You can determine this by looking at the Manage Storage pane in settings app (see below).
The warning you describe comes up when the expected size of the next backup is greater than the available free space.
You can reduce the size of the expected backup on iOS (updated for iOS 12) as follows:
- open the Settings app
- tap your AppleID/iCloud avatar (first item, top of list)
- tap iCloud
- tap Manage Storage
- tap Backups
- tap the name of the device in question (it usually says this iPod touch, this iPhone or this iPad to help if you have many devices connected to iCloud)
- look at Next Backup Size
- toggle off any unwanted apps from the list below
If that is less than the available space, you may need to contact Apple support to have your account fixed on the server side. In most cases, you can toggle off the largest few items and then attempt a backup when the estimate is less than the available space.
Once the backup is complete, you can tune the backups or manage your space as needed on iCloud.
In my case, I have the problem that iCloud estimates my data usage to be 10.9GB, while I have chosen to back up maybe only 1-2GB. If I turn, for example, camera roll off or on again, it doesn't matter.
iCloud estimates this wild, high, far too much space to make a backup, and I even deleted my previous backup and started new, to be sure to 'reset' everything, but it doesn't help!
My iPad only uses 2.2 GB, I have 2.8 left for the phone, and select 'no backup' for most, but the mail and a few programs like Skype and so on, altogether far less than "10.9" GB, probably only 1-2GB.
This problem seemingly happened before, the iCloud backup grow out of control, like a classical Windows installation.
However, I now see that, as I deactivate more and more smaller applications, of a few kb size of their data, that the total usage decrease much more than these few kb which are stated for each app.
This means that Apple seemingly underreports how much data they backup, from each app, or maybe the system counts too much, I don't know.
It is not possible to deactivate all the apps at once, in the hope to get down to the 17MB which is stated on the first page, (e-mail and settings), so there will be a lot of job to make this work again... :-/
The solution where you disable certain data from being backed up in iCloud is not really a solution but merely a workaround. Unfortunately, the real solution would imply you paying for iCloud's yearly subscription charges.
Or keep your iPhone backup out of the cloud an on your PC instead: There is not enough iCloud storage available. How to backup iPhone
Alternatively, keep the Camera Roll under iCloud backup settings disabled as that eats lots of space and back up your iPhone to your PC via iTunes. This way you don't lose the backup of your Camera Roll.
Are you sure you only need 120 MB for iCloud Backup?
Check the size of the 'next backup' in iCloud Backup on your device. Make sure that it's less than the free space of your iCloud account.
Are you checking the storage of the correct iCloud account?
Make sure that you're looking up the free space of the correct iCloud account if you have multiple. Only the main iCloud account can be used for iCloud Backup — accessible through Settings → iCloud.
For those who are still getting this problem with iOS 8 I tried using iCloud to backup for the first time (no data had been used). It said it couldn't as the backup would need 9.7gb. I tried just turning off the larger items but it was still at 7gb. Quite bizarre that you need to tap the off toggle AND THEN TAP DELETE IN A POPUP ALERT!!! I mean, who on earth do they have in their UI department nowadays? In my case I have about 500 (?) apps, each of which has to have the button toggled off and then the alert dismissed by tapping delete. This is quite bizarre as I had never turned all of these on AND there is no way that I could see of turning them all off to start with and then turning back on the ones I wanted. I presume that also means that for every app that I install from now on this will be set on and I will need to remember and explicitly turn it off.
I have now toggled off about a fifth of them (and it has taken an eternity!) but I am still at 5.2gb so I need to keep going. The supposed data size taken up by apps I am now down to is 1.8mb so obviously this has no relationship whatsoever to the size the iPad is intending to copy up to iCloud for the apps. I also have very slow internet so the prospect of waiting for 5gb to copy is laughable (probably months) so I'll need to go through all of them.
Time has passed and I am now maybe half way down and my finger is getting sore from tapping. This had better work!
Aahhrrgg!! The phone rang, I talked to my brother about my ailing parents, I returned and my iPad had gone to sleep. iCloud Backup had been turned off and it appears I am back to the beginning! I give up!!!! The next guy I speak to who compliments apple's developers in any way is probably going to get a good thrashing - I don't think they could program their way out of a simple do() while() loop.