What Time Should I go to Bed if I Wake up at 8 AM?

You should go to bed at 12:15 am for 5 sleep cycles or 10:45 pm for 6 sleep cycles.

Each sleep cycle lasts 90 minutes, and most people sleeps for 4 to 6 sleep cycles or 6 to 9 hours each night. It takes about 15 minutes for people to fall asleep which is also taken into account.

The when to wake up calculator calculates the ideal wake up time if you go to sleep now.