Health
Sleep Calculator
Calculate the ideal bedtime or wake-up time using 90-minute sleep cycles and an average 15-minute fall-asleep time.
About This Tool
Find the best time to go to bed or wake up based on complete 90-minute sleep cycles. The calculator also includes an average 15-minute fall-asleep period.
Sleep Cycle Method
sleep window = target time +/- (90 minutes x number of cycles) +/- fall-asleep timeThe calculator counts backward from a wake-up time or forward from a bedtime using 90-minute cycles and a default 15-minute time-to-fall-asleep assumption.
How To Interpret The Times
The suggested times are planning anchors, not medical rules. They aim to place wake-up time near the end of a sleep cycle, when many people feel less groggy.
Consistency matters as much as a single night. A regular bedtime, wake time, dark room, and reduced late caffeine usually have more impact than chasing a perfect cycle count.
When To Be Careful
If sleep problems are persistent, severe, or linked with breathing pauses, daytime impairment, pain, anxiety, or medication changes, use this calculator as a planning aid and speak with a clinician.
Examples
Wake up at 7:00 AM
Target wake time: 7:00 AM; fall-asleep estimate: 15 minutes
Result: The calculator suggests bedtimes aligned to complete 90-minute cycles before 7:00 AM.
Go to bed now
Bedtime mode with the current time
Result: Suggested wake-up times after several complete sleep cycles.
FAQ
How long is a sleep cycle?
A typical sleep cycle lasts around 90 minutes, although it varies slightly from person to person.
Why does the calculator add 15 minutes?
Most people don't fall asleep instantly. The calculator assumes an average of 15 minutes to fall asleep.
How many sleep cycles should adults get?
Most adults benefit from around 5 to 6 complete sleep cycles per night, depending on individual needs.
Important Note
Health calculators are general screening and education tools. They are not a diagnosis or medical advice. Speak with a qualified clinician for personal health decisions.