Why sleep cycles matter
During the night your brain moves through lighter and deeper stages of sleep in a repeating pattern. One full pattern is called a sleep cycle, and it lasts about 90 minutes on average. If your alarm goes off in the middle of deep sleep, you are more likely to feel heavy and groggy. Waking at the end of a cycle, when sleep is lighter, often feels easier.
How many cycles should you aim for?
Most adults do well with five or six cycles, which is 7.5 to 9 hours in bed after you have fallen asleep. Four cycles adds up to six hours. That can work for a night or two, but it is less than most adults need over time. Aim for seven or more hours on most nights.
Make the result work in real life
- Keep your wake-up time steady. A regular wake-up time, even at weekends, helps your body clock more than any single bedtime.
- Allow for winding down. The calculator tells you when to be asleep, so start your wind-down routine earlier. Our guide to fixing your sleep schedule shows how to move your bedtime gently.
- Be honest about how long you take to fall asleep. If it is closer to 30 minutes than 15, change the box above.
- Treat it as an estimate. Sleep cycles are not exactly 90 minutes for everyone, so adjust by 15 to 30 minutes if you still feel tired.
When to talk to a doctor
A calculator cannot fix a sleep problem. Speak to a doctor if you regularly struggle to fall asleep, wake often, snore loudly or feel very sleepy during the day despite spending enough time in bed.
