Health & Fitness · Wellbeing
Sleep Calculator — Bedtime and Wake-up Times by Sleep Cycles
Plan sleep around ~90-minute sleep cycles so you wake at the end of a cycle rather than in deep sleep. Enter the time you need to get up to see the best bedtimes, or your bedtime to see the best alarm times — allowing for the time it takes to fall asleep — and compare with the recommended hours for your age.
Your inputs
Quick start — try a typical case
Your result Live
Go to Bed At
10:45 PM
5 sleep cycles (7 h 30 min of sleep) + 15 min to fall asleep
- Other Good Bedtimes
- 9:15 PM (6 cycles) · 12:15 AM (4 cycles) · 1:45 AM (3 cycles)
- Recommended for You
- 7–9 hours a night (adult (26–64))
Bedtimes
4 rowsA regular schedule matters more than hitting a cycle boundary exactly. Ongoing trouble sleeping, loud snoring or daytime sleepiness are worth discussing with a doctor.
Population-average estimates for healthy adults, not medical advice. Talk to a doctor or registered dietitian before major changes to diet or exercise, or if you are pregnant or have a health condition.
How this is calculated
Bedtime = wake-up time − n × cycle length − time to fall asleep · Alarm = bedtime + time to fall asleep + n × cycle length
- n
- Number of complete sleep cycles (5–6 for most adults)
Through the night you pass through roughly 90-minute cycles of light, deep and REM sleep. Waking at the end of a cycle, when sleep is light, usually feels easier than being woken from deep sleep. Five cycles is 7.5 hours and six is 9 — both inside the 7–9 hours recommended for adults.
Assumptions & sources
- Cycles of equal length; real cycles vary between people and through the night.
- 1National Sleep Foundation's sleep time duration recommendations (Hirshkowitz et al.) — Sleep Health 1(1), 2015
- 2Sleep duration — why does it matter? — Human Performance Resources by CHAMP (Uniformed Services University)
Calculator ID HLTH-SLEEP-001 · version 1.0.0
Common questions
What time should I go to bed to wake up at 6:30?
About 10:45 PM (5 cycles, 7.5 hours) or 9:15 PM (6 cycles, 9 hours), allowing 15 minutes to fall asleep.
How long is a sleep cycle?
About 90 minutes on average, ranging from roughly 70 to 120 minutes.
How much sleep do adults need?
7 to 9 hours a night for adults under 65, and 7 to 8 for those 65 and over.