What is a sleep cycle?
A sleep cycle is a repeating pattern of lighter sleep, deeper sleep, and REM sleep. Many calculators estimate cycles around 90 minutes, but real cycles vary by person and night.
Sleep timing answers
Sleep Cycle FAQ
A plain-English FAQ for people using sleep calculators to plan wake-up times, naps, caffeine cutoff, and better routines.
Quick answer: A sleep cycle is a repeating pattern of lighter sleep, deeper sleep, and REM sleep. Many calculators estimate cycles around 90 minutes, but real cycles vary by person and night.
Why do calculators suggest wake-up windows?
Wake-up windows try to avoid waking you from deep sleep. They are estimates, not medical measurements, so use them as planning guidance rather than exact science.
How long should a nap be?
A short nap of about 10 to 25 minutes can reduce grogginess for many people. A longer nap may help if you have enough time to complete a fuller sleep cycle.
When should I stop caffeine?
A conservative cutoff is 8 to 10 hours before bedtime. People who are sensitive to caffeine may need an earlier cutoff.
Can sleep calculators fix insomnia?
No. Calculators can support routines, but persistent insomnia, breathing issues, or major daytime sleepiness should be discussed with a qualified clinician.
What is the best first change for better sleep?
Keep a consistent wake time, get morning light, reduce late caffeine, and make bedtime easier to repeat.