Sleep & Energy
Sleep calculator
Find the best time to go to bed or wake up, based on 90-minute sleep cycles and about 15 minutes to fall asleep.
Times include about 15 minutes to fall asleep. Aim for 5–6 cycles (7.5–9 hours).
How the sleep calculator works
During the night, your brain moves through sleep cycles of roughly 90 minutes: light sleep, deep sleep and REM sleep. Waking up at the end of a cycle, when sleep is lighter, usually feels easier than being pulled out of deep sleep by an alarm. The calculator counts back (or forward) in 90-minute steps and adds about 15 minutes for falling asleep.
How to use the results
- Choose 5 or 6 cycles. That is 7.5–9 hours, in line with the recommendation that adults sleep at least 7 hours a night.
- Keep the wake time fixed. A consistent wake time, weekends included, is the most reliable way to fall asleep and wake up more easily.
- Treat it as a guide. Cycle length varies between people and during the night (roughly 80–110 minutes), so adjust by 15 minutes if you still wake up groggy.
Frequently asked questions
How long is one sleep cycle?
About 90 minutes on average, although it varies from roughly 80 to 110 minutes between people and across the night. Early cycles contain more deep sleep, later ones more REM sleep.
How many sleep cycles do I need?
Most adults need 5–6 cycles, which is 7.5–9 hours. The American Academy of Sleep Medicine recommends at least 7 hours of sleep per night for adults.
What time should I go to bed to wake up at 7 a.m.?
For 5 or 6 full cycles plus 15 minutes to fall asleep, go to bed at about 9:45 p.m. or 11:15 p.m.
