I kept waking up tired even after 7 or 8 hours of sleep.

turns out that timing matters just as much as duration. If your alarm goes off in the middle of a cycle, you feel awful regardless of how long you slept.

So I built this. You enter your bedtime, it factors in about 15 minutes to fall asleep, then shows you wake-up times aligned to the end of each 90-minute sleep cycle.

These times are when it’s easiest to wake from.

Just a web page I load up every few evenings now when starting at the clock at 2am or have to get up earlier..