For every 8 hours at work, how much time do you spend doing nothing useful?

[EpicRandy]

At my current job I would say between 15 -20 minutes not counting breaks. But at my previous job I was able to lost between 1h 30m to 2h 30m easily due to extremly long process such as compiling a game that was taking up to 45m while you almost can't do anything.