Time Machine large backup

[thewall]

I have just migrated all my data (t/m unplugged) from iMac to iMac and the T/M had only 50gb left out of 1tb.

I erased the external hd and now i'm starting from fresh but it says it is backing up 437gb why? when i look at about this mac i have 705gb left from 1tb where has the other 130gb come from.

 

[Kissmyne]

Do you have any external drives or devices plugged in? I've seen Time Machine "auto select" all drives not set for Time Machine backups.. i.e. if you do have other drives or devices with media storage attached... either disconnect them or add them to the Time Machine exclusion list if this is the case.

If this doesn't resolve the issue, Please provide OS X version, as well as screenshots of your Time Machine preferences window(s).

 

[thewall]

OSX El Capitain no external hd

 

[Kissmyne]

If you look at your final screenshot, The drive capacity(Macintosh HD) is showing 1.11 TB and free is 705 GB. 1.11 TB converts to approx 1136 GB(~1.2 TB unformatted capacity), the difference between capacity and free in your screenshot being about 430 GB give or take. This is looking like expected behavior, as the math generally supports the size of the backup.