IME it's fairly variable day-to-day; four is probably about the median but two or fewer is not uncommon, I use those days to get caught up on easier tasks. What

IME it's fairly variable day-to-day; four is probably about the median but two or fewer is not uncommon, I use those days to get caught up on easier tasks. What you're describing is completely normal and shouldn't cause distress. > How can I take the number of hours I can work on hard coding problems towards the number of hours I can be awake? Honestly I would say this shouldn't be a goal, even directionally. Do your best to optimise your space and time for focused work, and if it ends up that you're regularly able to sustain a whole day of focused work that's good, but even if you can't that's still the best you can do. To that end, you'll really have to experiment with what works best for you. Sounds like you're getting good results in your work periods so start with what you're doing outside of them: diet, sleep, recreation, etc all have a sizeable impact on your ability to do good work.