Sleep calculator: what time should I go to bed?

I want to…

Go to bed at one of these times

  • 21:45Recommended

    6 cycles · 9 h of sleep

  • 23:15Recommended

    5 cycles · 7 h 30 min of sleep

  • 00:45

    4 cycles · 6 h of sleep

  • 02:15

    3 cycles · 4 h 30 min of sleep

For adults, 5 or 6 cycles (7.5 to 9 hours of sleep) are recommended.

A cycle lasts about 90 minutes on average, but anywhere from 70 to 120 minutes depending on the person and the time of night. These times are a guide and are not medical advice.

How to use this calculator?

1. Choose whether you need a bedtime (for a fixed alarm) or a wake-up time (based on when you go to bed)
2. Enter the time, or click "I'm going to bed now"
3. Adjust how long you take to fall asleep, 15 minutes on average
4. Preferably pick a time marked "Recommended", meaning 5 or 6 full cycles

Quick answer

What time should I go to bed to wake up at 7:00?

Start from your wake-up time, take away the time you need to fall asleep (about 15 minutes), then 90 minute cycles. To wake up at 7:00: 7:00 − 15 min − 5 × 1 h 30 = 23:15, or 21:45 for 6 cycles. These are the two times recommended for adults.

Cycles (sleep)Bedtime to wake up at 7:00
6 cycles (9 h)21:45
5 cycles (7 h 30)23:15
4 cycles (6 h)00:45
3 cycles (4 h 30)02:15

About the Sleep Cycle Calculator

What is it?

This calculator tells you when to go to bed so you wake up at the end of a sleep cycle, or when to set your alarm based on when you go to bed. It suggests 3 to 6 full cycles and highlights the durations recommended for adults.

Why use it?

Waking up in the middle of a cycle, during deep sleep, is what makes you feel groggy. Aiming for the end of a cycle helps you get up more easily, even after a slightly shorter night.

How does it work?

Sleep is organised in cycles of about 90 minutes (light sleep, deep sleep, then REM sleep). The tool adds the time you take to fall asleep (15 minutes by default) and counts multiples of 90 minutes: bedtime = wake-up time − time to fall asleep − n × 90 min, or wake-up time = bedtime + time to fall asleep + n × 90 min. Times that cross midnight are handled automatically.

Usage tips

  • To wake up at 7:00, go to bed around 23:15 (5 cycles) or 21:45 (6 cycles)
  • Keep regular hours, even at weekends: it is the best way to sleep well
  • Cycle length varies from person to person: shift by 10 to 15 minutes if you wake up tired
  • Avoid screens and caffeine in the hour before bed
  • If you are always tired or cannot sleep, talk to your doctor
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