Frequently Asked Questions
How many hours of sleep do I need?+
Adults need 7-9 hours (5-6 sleep cycles). Teens need 8-10 hours. Children need 9-12 hours. Quality matters as much as quantity.
What is a sleep cycle?+
A sleep cycle is approximately 90 minutes and includes light sleep, deep sleep, and REM (rapid eye movement) sleep. Most people complete 4-6 cycles per night.
Why do I feel groggy even after 8 hours?+
You may have woken up in the middle of a deep sleep cycle. This is called sleep inertia. Use the calculator to time waking up at the end of a cycle.
What is the best time to wake up?+
The best wake-up time is at the end of a sleep cycle. The calculator helps you find times that align with cycle endings for your planned bedtime.
Can I catch up on lost sleep on weekends?+
Research shows you can partially recover from sleep debt but you cannot fully catch up. Consistent sleep schedules are much better than irregular sleeping patterns.