Sleep CycleCalculator
Work out when to go to bed or set your alarm so you wake up between sleep cycles, not in the middle of one.
How it works
A night of sleep is made of repeating cycles of light, deep and REM sleep. Each cycle lasts about 90 minutes for most adults, though it can vary from around 70 to 120 minutes. Waking at the end of a cycle, when sleep is lightest, usually feels easier than waking from deep sleep. This is why 7.5 hours can feel better than 8.
Most adults need 7 to 9 hours a night, according to guidance from the US National Sleep Foundation and the NHS. To find a bedtime, count back from your wake-up time in 90-minute blocks, then add about 15 minutes to fall asleep. For a 7:00 am alarm, that gives bedtimes of 9:45 pm, 11:15 pm or 12:45 am.
sleepcycle.tools brings together simple calculators that each do one job: bedtimes, wake-up times, naps, sleep debt, baby sleep schedules and jet lag. Every calculation happens in your browser, and you don't need an account.
Tools on the way
Bedtime calculator
When to go to bed for a set wake-up time.
Wake-up calculator
The best alarm time if you go to bed now.
Nap calculator
How long to nap and when to wake up.
Power nap timer
10, 20 and 30 minute nap timers.
Sleep debt calculator
How much sleep you owe after a short week.
Sleep needs by age
Recommended hours from newborn to older adult.
Baby sleep schedule
Naps and wake windows month by month.
Caffeine cutoff calculator
When your last coffee should be.
Jet lag planner
Shift your sleep before and after you fly.
Night shift sleep planner
A sleep plan around rotating shifts.
White, pink and brown noise
Noise played in your browser.
Questions
How long is one sleep cycle?
About 90 minutes on average for adults, with a usual range of 70 to 120 minutes. Cycles early in the night have more deep sleep, and later ones have more REM sleep.
Is 6 hours of sleep enough?
For most adults it is less than the recommended 7 to 9 hours. A small number of people do need less, but regularly sleeping 6 hours or less is linked with poorer health.
These tools give general information, not medical advice. If you have ongoing sleep problems, talk to a doctor.