Free tool
Sleep cycle calculator
Find a bedtime for the time you need to get up, or wake-up times for when you go to bed, based on roughly 90-minute sleep cycles.
Suggested bedtimes
Bedtime
8:45 PM
6 cycles · 9h of sleep
Meets the CDC's 7+ hours for adults
Bedtime
10:15 PM
5 cycles · 7h 30m of sleep
Meets the CDC's 7+ hours for adults
Bedtime
11:45 PM
4 cycles · 6h of sleep
Under the 7+ hours recommended for adults
Educational estimate, not medical advice. Talk to your doctor before making changes, especially if you have a health condition, take medication, or are pregnant.
How this works
Sleep moves through stages (light sleep, deep sleep and REM sleep) in repeating cycles of roughly 90 minutes. Cycle length varies between people and across the night, so you can adjust it from 80 to 110 minutes.
For bedtimes, we take your wake-up time, subtract the time it takes you to fall asleep, then subtract 4, 5 or 6 full cycles (about 6, 7.5 or 9 hours). For wake-up times, we add them instead. Times can cross midnight.
Waking at the end of a cycle may feel easier for some people, but evidence on cycle-timed waking is limited. Treat these times as a starting point, not a rule.
Limitations
- Real sleep cycles vary in length and aren't perfectly regular through the night.
- The calculator can't tell how well you sleep or whether you have a sleep problem.
- It's meant for adults; children and teenagers need more sleep.
- Shift work, jet lag and new parenthood may need a different approach; talk to your doctor.
Privacy
Tool inputs stay on your device. Everything is calculated in your browser; nothing you enter is sent to us or stored, apart from optional preferences (such as units or your last schedule) saved in your own browser.
Frequently asked questions
What is a sleep cycle and how long does it last?
A sleep cycle is a progression through different sleep stages, including non-REM and REM sleep. Cycle length varies within a night and between people, so a fixed duration is a simplification. A calculator can suggest possible clock times, but it cannot measure your stages or guarantee how you will feel.
What is a sleep cycle for an adult?
Adult sleep moves through non-REM and REM stages repeatedly during the night. Those stages are not evenly divided or identical each time, and ordinary clock arithmetic cannot tell which stage you are in. Use estimated bedtime options as planning ideas rather than a measurement of your sleep or a medical assessment.
How much sleep do I need a night?
Sleep needs vary with age and individual circumstances, and time in bed is not always time asleep. The CDC provides age-based guidance for adults and other age groups. Use that guidance as a starting point, not a calculator-generated prescription, and discuss persistent daytime sleepiness or sleep difficulties with your doctor.
Is sleeping 6 hours enough?
For most adults, six hours is below the general sleep duration guidance described by the CDC. An occasional short night and a regular pattern are different situations. How you feel does not establish a diagnosis. Discuss persistent tiredness, disrupted sleep or difficulty allowing enough time for sleep with your healthcare provider.
What is sleep debt?
Sleep debt is a shorthand for the difference between the sleep someone needs and the sleep they get over time. The idea is useful for discussing short nights, but a simple total is not a measurement of your personal needs. It cannot establish a condition or an exact catch-up schedule.
Can you catch up on sleep on weekends?
Sleeping longer on weekends does not provide a precise accounting system for a week of short nights. Sleep duration, timing and individual needs all matter, so there is no exact catch-up formula here. Consider how consistently you allow time for sleep, and discuss ongoing tiredness or sleep concerns with your doctor.
Sources
- CDC: About Sleep
- Watson NF et al. (2015). Recommended amount of sleep for a healthy adult: a joint consensus statement of the AASM and SRS. Sleep.
- NINDS: Brain Basics: Understanding Sleep
- Sleep Foundation: Stages of Sleep
- NIGMS: Circadian Rhythms
- Edinger JD et al. (2021). Behavioral and psychological treatments for chronic insomnia disorder in adults: an AASM clinical practice guideline. J Clin Sleep Med.
Last reviewed by the Body Reset Guides editorial team