90 minutes is a default
Sleep cycles vary. The U.S. National Heart, Lung, and Blood Institute describes cycles that restart roughly every 80–100 minutes. We use 90 minutes as an adjustable midpoint, not as an exact biological clock.
SLEEPY ORBIT • FREE CALCULATOR
Find a calmer time to sleep or wake.
Plan around estimated sleep cycles without sign-ups, apps or hidden calculations. Choose when you need to wake, when you plan to sleep, or calculate from right now.
☾ Adjustable cycles
◌ Age guidance
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Sleep Calculator
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YOUR SLEEP WINDOWS
Suggested times
Sleep stages are not perfectly timed. These results are planning estimates, not measurements of your individual sleep.
HOW IT WORKS
Simple math. Transparent assumptions.
Instead of pretending there is one scientifically perfect bedtime, the calculator shows several possible sleep windows and lets you change the numbers behind the calculation.
Fall-asleep time is adjustable
The initial 15-minute buffer is simply a useful starting value. If you normally fall asleep faster or slower, move the slider and every result recalculates.
Multiple cycles, not one magic time
NHLBI says people usually experience four to six sleep cycles during a night. We display several cycle counts so you can compare durations rather than receive a single overconfident answer.
THE FORMULA
See exactly what the calculator does.
For a chosen wake-up time, we count backward:
Wake time − fall-asleep buffer −
(cycles × estimated cycle length)
For a chosen bedtime, we add the fall-asleep buffer and then count forward through the same cycle estimates.
Read the full methodology →
SLEEP DURATION BY AGE
Duration matters more than chasing a perfect cycle boundary.
CDC sleep-duration guidance changes with age. The calculator uses these ranges only as context for the duration of each result.
| Age | CDC daily sleep guidance |
|---|---|
| 13–17 years | 8–10 hours |
| 18–60 years | 7 or more hours |
| 61–64 years | 7–9 hours |
| 65+ years | 7–8 hours |
COMMON QUESTIONS
Sleep calculator FAQ
Are sleep cycles exactly 90 minutes?
No. Cycle length varies between people and across the night. The calculator uses 90 minutes as a convenient default and lets you adjust it between 80 and 100 minutes.
Does waking at a calculated time guarantee I will feel refreshed?
No. A calculator cannot know your actual sleep stage without measuring sleep. Sleep quality, duration, illness, stress, schedule and many other factors can affect how you feel.
Why does the calculator include time to fall asleep?
Your sleep duration starts after you actually fall asleep rather than when you get into bed. The buffer is adjustable so you can use a value that better reflects your routine.
Do I need to create an account?
No. The calculator runs directly in the browser and ordinary calculations require no account.
Is this medical advice?
No. Sleep Calculator is a scheduling and educational tool. Persistent sleep problems, significant daytime sleepiness, breathing problems during sleep or other health concerns should be discussed with a qualified healthcare professional.
Built around transparent public-health sources.
Sleep-stage and cycle information: National Heart, Lung, and Blood Institute .
Age-based sleep-duration guidance: U.S. Centers for Disease Control and Prevention .
Source guidance describes populations and typical sleep patterns. It cannot determine an individual's exact sleep stage or ideal bedtime.