Calculate your optimal bedtime or wake-up time based on 90-minute sleep cycles. Wake up feeling refreshed by timing your sleep with your natural REM cycles.
Sleep occurs in cycles of approximately 90 minutes. Each cycle includes stages of light sleep, deep sleep, and REM (rapid eye movement) sleep. Waking up at the end of a complete cycle, rather than in the middle of one, helps you feel more rested and alert.
Most adults need 5 to 6 complete sleep cycles per night, which equals 7.5 to 9 hours of sleep. However, individual needs vary. Some people function well on 4 cycles (6 hours), while others need 7 cycles (10.5 hours). The key is to find what works best for your body and to wake up at the end of a cycle.
Sleeping for 7.5 hours (5 cycles) can leave you feeling more refreshed than sleeping 8 hours, because 8 hours means you wake up during the middle of a sleep cycle. This calculator helps you align your schedule with your natural sleep rhythms for optimal rest.
Keep the schedule
Finding the time is the easy half. Going to bed at it on a Wednesday is the other one. Log lights-out as a habit, write a line about how the night actually went, and let the streak do the arguing for you.
The free plan is free forever and takes no card. Pro is $4.99/mo or $49.99/yr; its 7-day trial does ask for a card and charges nothing for 7 days.