That being said, I don't worry about tracking bathroom breaks, or the occasional mental break here and there. My client is happy, I'm getting done what they're wanting to get done when they're wanting it to be done, I just bill 8 hours for the day and it's not a big deal (obviously it isn't, they've been willing to pay for me for almost three years at this point on two different projects and I get glowing reviews whenever I request feedback from them to pass along to my boss).
I work 8:30 to 5:30 so that includes an extra hour for lunch, by the way, so that's not counted, no. But I'm at home, so it doesn't feel like work anyway, just an hour to relax, have a sandwich, let the dogs out, and maybe throw a recipe in the slow cooker for dinner.
I'm actually in the middle of a 3.5 week break because I had so much built up time at the end of the year. I knew my client does a two week furlough for consultants at the end of the year so I was already planning for that, and also was planning a week for a wedding trip for a wedding ceremony/reception that had to be cancelled because a recent hurricane pretty much destroyed the town it was going to be held in. And I took a week off for vacation earlier this year.
Where I am now we're not expected to bill quite as much for this reason. Although I did once work somewhere where there was a requirement for 2250 hours/year billed. Which doesn't seem *to* bad until you take PTO into account and the aforementioned bio breaks.