Sleep Calculator: When Should I Go to Bed?
Work out the best time to fall asleep or wake up so your alarm lands at the end of a sleep cycle rather than in the middle of deep sleep.
Timings are estimates based on average cycle length. If you regularly feel unrested, speak to a doctor.
How the sleep calculator works
Through the night, sleep moves through repeating cycles of light sleep, deep sleep and REM (dream) sleep. Each cycle lasts about 90 minutes on average. Waking up at the end of a cycle, when sleep is lightest, can feel easier than being woken from deep sleep.
The calculator counts back (or forward) in 90-minute blocks from the time you enter and adds the time it usually takes you to fall asleep. Six cycles is 9 hours of sleep, five is 7.5 hours, and four is 6 hours, which is less than the 7 hours or more recommended for adults.
Other things that help you sleep better
- Keep a regular sleep and wake time, including at weekends.
- Keep the bedroom cool, dark and quiet. If you sleep hot, see our best cooling mattresses and tips for sleeping cooler.
- Make sure your mattress suits your sleeping position. Our mattress quiz can help.
FAQs
How long is a sleep cycle?
A full sleep cycle lasts roughly 90 minutes on average, although it can range from about 70 to 120 minutes and varies through the night and from person to person. Most adults go through four to six cycles a night.
How many hours of sleep do adults need?
Major sleep and health organisations recommend that adults get at least 7 hours of sleep per night on a regular basis. Teenagers and children need more.
Why do I feel groggy even after a full night’s sleep?
Waking during deep sleep can leave you feeling groggy (sleep inertia). Timing your alarm for the end of a cycle may help, but consistent sleep and wake times matter more than precise cycle timing.
How long does it take to fall asleep?
Most healthy adults fall asleep in roughly 10 to 20 minutes. This calculator assumes 15 minutes; you can change it to match you.