Tell us when you need to get up and we'll suggest bedtimes that end on a full sleep cycle — or find when to wake if you go to bed now.
The working
How the sleep calculator works
Sleep comes in cycles of roughly 90 minutes. Waking at the end of a cycle, when sleep is lightest, is usually easier than waking in the middle of deep sleep, so the calculator works backwards (or forwards) in whole cycles, allowing 15 minutes to fall asleep.
bedtime = wake-up time − cycles × 90 min − 15 min
Example: to wake at 7:00 am, going to bed at 9:45 pm gives six cycles (9 hours), 11:15 pm gives five (7½ hours) and 12:45 am gives four (6 hours).
How many cycles to aim for
Cycles
Sleep
Good for
6
9 hours
Catching up, teenagers
5
7½ hours
Most adults, most nights
4
6 hours
An occasional short night
3
4½ hours
Emergencies only
Tips for waking up refreshed
Keep a regular wake-up time, even at weekends; your body clock settles around it.
Get daylight soon after waking, and keep screens dim in the hour before bed.
Cut caffeine from the afternoon: it can stay in your system for many hours.
This calculator is a guide, not medical advice. Ongoing sleep problems are worth discussing with a doctor.
Questions people ask
What is a sleep cycle?+
Through the night you move through light sleep, deep sleep and REM (dreaming) sleep in a repeating cycle that lasts about 90 minutes on average. Waking at the end of a cycle, when sleep is lighter, tends to feel easier than being woken from deep sleep.
How much sleep do I need?+
Most adults need around 7 to 9 hours a night — five or six full cycles. Teenagers and children need more. If you regularly feel tired despite enough sleep, it's worth talking to a doctor.
Why does the calculator add 15 minutes?+
Most people take 10 to 20 minutes to fall asleep, so the calculator allows 15 minutes before the first cycle starts. If you usually drop off faster or slower, shift the times to suit.
Are sleep cycles always 90 minutes?+
No — they vary from person to person and through the night, typically between 70 and 120 minutes. Ninety minutes is a useful average, so treat the suggested times as a good starting point rather than exact.