I recently read the book Why We Sleep by Matthew Walker (a professor at Berkeley). It's pop-sciency in style but more nuanced and well-supported than most pop science books I've read. I definitely recommend picking it up. It made me value sleep a lot more than I used to, both for long- and short-term reasons.

Among other things, the book talks about how much sleep people need. Almost everyone needs around 8 hours—it varies with age, but it pretty consistent among people at the same with very rare exceptions. For most people, being short even by just one hour (ie a night with seven hours of sleep) has a number of measurable negative effects.

https://smile.amazon.com/Why-We-Sleep-Unlocking-Dreams/dp/15...

I'm no expert, but from what I've read you should awaken without feeling groggy or tired. I've personally had the luxury of being able to sleep according to my own schedule (without waking times or alarms, simply sleeping when I was tired). For myself to reach that well-rested feeling, I should give myself 9 hours a night. Sometimes I need 7, but sometimes I need the 9 hours. I very occasionally need more, and very rarely sleep less (though it happens).

What I know affects how much sleep I need or how long I should give myself to sleep varies. I'm female and follow a cycle closely linked to hormones as a baseline. If I wake up at night (for toilet, etc), I need a bit more time. If I increase physical activity, I have an adjustment period that requires more sleep.

I'll also note that time of sleep impacts me. I'm better off waking after 9am (naturally this is 11am or so). I cannot always get enough quality sleep waking at 6am and 7am leaves me slightly deprived. I tried keeping a schedule even on the weekends, but I felt horrible and found it better to sleep a bit more to catch up.

Test out what happens to you when you alter sleep habits. How much uninterrupted sleep do you prefer and when? What are the effects of naps during the day on metrics you care about? Keep the traditional sleep log, and track your other related behaviors & habits like eating/nutrition, exercise, etc. National averages are useful, but nothing beats learning how our own bodies function in various situations.

Here is one example paper https://www.ncbi.nlm.nih.gov/pubmed/28545315 and while it isn't a direct example of how to find your own ideal sleep patterns, it does highlight the relationship between sleep and body weight in the study population and it again mentions the 6-8 hour recommended minimum sleep period. This source might be better https://www.sleepfoundation.org/excessivesleepiness/content/...

I'm by far no expert on this, just listened to a lot of podcasts and read articles. So, grain of salt etc...

AFAIK the only way to be sure is to either go to a sleep lab, or get an accurate tracker like the Oura ring, which reportedly has a 80-90% accuracy compared to sleep lab data. With that data you can see the distribution of your various sleep phases, and the people in the lab or the app will tell you how much of each phase you'd ideally have.

But, why not just experiment a bit? Sleep 7/8/8.5h for a couple of days in a row, and keep track of how you feel and how much you procrastinate. E.g. for Mac, the Timing app is great at tracking how much time you spend in each app - one could use the amount of "productive" apps (text editor, IDE, graphical editor...) as a measure of productivity.