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Sleep calculator

Calculate the best time to sleep or wake up based on sleep cycles. Wake up refreshed.

If I want to wake up at 10:30, I should sleep at

Results

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What is a sleep cycle?

When you sleep, your body and brain go through several sleep cycles. Each cycle consists of 4 stages: three of NREM sleep (no rapid eye movement) and one of REM sleep (rapid eye movement).

Cycle duration

Each sleep cycle lasts approximately 90 minutes. An adult needs 5-6 cycles per night (7.5-9 hours).

Sleep stages

NREM 1 Wake-sleep transition
NREM 2 Light sleep
NREM 3 Deep sleep (recovery)
REM Dreams and consolidation

Recommended sleep hours by age

Age Recommended hours
0-3 months 14-17h
4-11 months 12-15h
1-2 years 11-14h
3-5 years 10-13h
6-13 years 9-11h
14-17 years 8-10h
18-65 years 7-9h
> 65 years 7-8h

Why is sleeping well important?

Determining a sleep schedule will allow you to rest the necessary hours to perform with energy during the day. Sleeping little or poorly can have negative consequences for both mental and physical health.

How does the calculator work?

The calculator uses 90-minute cycles and adds 15 minutes to fall asleep. Choose whether you want to know what time to go to bed (to wake up at X time) or what time to wake up (if you go to bed at X time). It will show you multiple options with 3 to 6 cycles (4.5h to 9h).

  • 90-minute cycles: calculates according to sleep science
  • Multiple options: from 3 to 6 cycles (4.5h to 9h)
  • Age recommendations: complete table from 0 to 65+ years
  • Two modes: calculate sleep or wake time
  • Free: online calculator available 24/7
  • Science-based: NREM and REM sleep phases

Frequently Asked Questions

How long is a sleep cycle?
Each sleep cycle lasts approximately 90 minutes. An adult normally completes 5 to 6 cycles per night, which equals 7.5-9 hours of sleep.
What is the best time to sleep?
Scientists recommend not going to bed after 11:30 PM. To enjoy optimal sleep time (between 7 and 9 hours) and wake up between 7-8 AM, the ideal is to go to bed between 10:00 PM and 11:30 PM.
How many hours of sleep do I need according to my age?
Needs vary by age: 0-3 months: 14-17h, 4-11 months: 12-15h, 1-2 years: 11-14h, 3-5 years: 10-13h, 6-13 years: 9-11h, 14-17 years: 8-10h, 18-65 years: 7-9h, over 65 years: 7-8h.
What are the sleep phases?
Sleep has 4 phases: NREM 1 (wake-sleep transition), NREM 2 (light sleep), NREM 3 (deep restorative sleep), and REM (rapid eye movement sleep where dreams occur).
Why is waking up between cycles better?
Waking up at the end of a complete sleep cycle (not in the middle) helps you feel more rested and alert. Interrupting a cycle, especially during deep sleep, can cause a feeling of grogginess.
How do I calculate my sleep hours?
Use our calculator: select whether you want to know what time to sleep (to wake up at X time) or what time to wake up (if you go to bed at X time). The calculator will show you the best options based on 90-minute cycles.
What happens if I sleep less than 7 hours?
Sleeping less than 7 hours regularly can increase the risk of chronic diseases (hypertension, type 2 diabetes, obesity, depression), weaken the immune system, affect mood and reduce cognitive capacity.
How long does it take to fall asleep?
Most people take between 10-20 minutes to fall asleep. Our calculator automatically adds 15 minutes to account for this preparation time.