Sleep Calculator

Calculate when to go to sleep to wake up rejuvinated
Get it on Google Play

How does it work?

The sleep calculator above helps you to pick the best possible hour to wake up allowing you to get several 90 minute sleep cycles. There are several ways to use Sleepty:

  1. If you are going to sleep now, you can calculate the optimal time to wake up. It answers the question, "When should I wake up if I am going to sleep now?"
  2. If you need to wake up at a specific hour, it will tell you when it is better to go to bed. It answers the question, "When should I wake up if I go to sleep now?"

Sleep cycle alarm clock app for Android

If you have an Android device, you can download a mobile app from AppStore. The app has features like:

  1. Bedtime calculator
  2. Wake up time calculator
  3. Gentle alarm. 10 minutes before you need to wake up, it will start playing ambient sounds of chirping birds to make it easier for you to slowly wake up. Then, when it is time to wake up, the app will play the alarm.
  4. Bedtime alarm. The app will notify you when it is time to go to bed.

Sleep cycles and stages

One would think that sleeping is a simple process - you go to bed and wake up fully refreshed. But in reality, sleeping follows a specific pattern, switching between deep sleep and REM sleep. These sleep phases form a cycle which occurs for approximately 90 minutes.

Non-REM sleep

NREM sleep is divided into three stages.

Stage 1

This stage is also called "transitional sleep" or "light sleep". During Non-REM, body temperature, heart rate, breathing rate decrease. Also, during this stage, people have slow eye movements. Your body starts preparing you for sleep.

Stage 2

No eye movement occurs in this stage. It is very easy to wake a person up.

Stage 3

This stage is commonly associated with deep sleep. During deep sleep it is extremely difficult to wake up.

REM sleep

REM sleep is known for occurrence of dreams. It takes approximately 70 to 90 minutes to get there after falling asleep.


Usually it is way easier to wake up during slow-wave sleep which occurs soon after the end of a REM phase.

How much sleep is recommended to get?

According to some studies, people who live the longest self-report sleeping for 6-7 hours each night. Of course, it all depends on an individual's physiology and age.