Sleep Cycle Calculator
Wake up refreshed by timing your sleep to 90-minute cycles.
Includes 14-minute average fall-asleep time
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Frequently Asked Questions
What is a sleep cycle?
A sleep cycle lasts approximately 90 minutes and includes light sleep, deep sleep (slow-wave), and REM (rapid eye movement) sleep. Most adults cycle through 4–6 of these per night. Waking up at the end of a cycle — rather than mid-cycle — leaves you feeling more rested and alert.
How many hours of sleep do I need?
Adults generally need 7–9 hours per night (4–6 complete sleep cycles). Teens need 8–10 hours, school-age children 9–12 hours. Consistently getting fewer than 7 hours is linked to increased risk of obesity, diabetes, cardiovascular disease, and impaired cognitive function.
What happens during REM sleep?
REM (Rapid Eye Movement) sleep is when most vivid dreaming occurs. Your brain is highly active, processing emotions and consolidating memories. REM sleep is critical for creativity, learning, and emotional health. It typically makes up 20–25% of total sleep time and increases in proportion during the later cycles of the night.