How can I tell when my body is ready to sleep?

Question

The problem is, due to caffeine usage I often end up going to bed too early and wasting time trying to fall asleep.

Are there any methods to find out whether my body is ready to fall asleep?

I would really like to avoid wasting these big chunks of time between going to bed and actually falling asleep.

Answer 1

The half life of caffeine is around 6 hours for an adult. So if you drink a cup of coffee at 3 PM, half of it will still be in your system if you try to fall asleep at 9 PM. Hence the recommendation to you is to stop drinking coffee well before afternoon.