Sleep Time Calculator
It's not just about how much you sleep, it's about *when* you wake up. Waking up during a deep sleep phase leads to morning grogginess. Our tool helps you time your wake-up call with the end of a natural sleep cycle.
You should go to bed at one of these times:
21:45
6 Cycles (9.0 hrs)
23:15
5 Cycles (7.5 hrs)
00:45
4 Cycles (6.0 hrs)
02:15
3 Cycles (4.5 hrs)
Sleep cycles last roughly 90 minutes. Waking up in the middle of a cycle makes you feel groggy. Waking up at the end of a cycle makes you feel energized!
Frequently Asked Questions
What is a sleep cycle?
A sleep cycle typically lasts about 90 minutes. During this time, you move through four stages of sleep, ending with REM (Rapid Eye Movement) sleep.
Why 90 minutes?
While it varies slightly per person, 90 minutes is the average length for a full human sleep cycle. Waking up at the end of these intervals is optimal.
How much sleep do I need?
Most adults need 5 to 6 full cycles per night (7.5 to 9 hours). However, even 4 cycles (6 hours) can feel better if you wake up at the right time.
Does it account for falling asleep?
Yes. This calculator adds 15 minutes to your bedtime to account for the average time it takes a healthy adult to drift off.