Today I am sitting on my desk with a pen and a notepad next to me and writing down everything I do and the time it takes me, so I can understand why I keep reaching the end of the day and not move forward with what I had planned for the day.

So, my conclusion is: on average for every hour I spend "working" 20 minutes are lost. From breaks, phone calls, random searches I do online, etc.

So, on an 8 hour work day, just around 5 are actually productive.