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Sleep Calculator
Find the best bedtimes based on 90-minute sleep cycles for better rest.
⭐ Used by 9,450 people

The Sleep Calculator finds the best bedtime for you based on 90-minute sleep cycles. Waking up at the end of a complete cycle makes you feel refreshed, not groggy!

How Sleep Cycles Work

  • 😴 Stage 1: Light sleep (1-5 mins)
  • 😴 Stage 2: Light sleep, body temperature drops (10-25 mins)
  • 😴 Stage 3: Deep sleep — most restorative (20-40 mins)
  • 🌙 Stage 4: REM sleep — dreaming, memory consolidation
  • ⏱️ One complete cycle = ~90 minutes

Recommended Sleep by Age

Age GroupSleep Needed
Newborns (0-3 months)14-17 hours
School kids (6-13)9-11 hours
Teenagers (14-17)8-10 hours
Adults (18-64)7-9 hours
Seniors (65+)7-8 hours

Tips for Better Sleep

  • 📵 No phone 30 mins before bed
  • 🌡️ Keep room cool (18-22°C ideal)
  • ⏰ Sleep and wake at same time daily
  • ☕ No caffeine after 2 PM
  • 🏃 Exercise but not within 2 hours of bedtime
📖 Complete Guide
Formulas, examples, tips & FAQs
Read Article →

Frequently Asked Questions

How does the sleep calculator work?

It works around 90-minute sleep cycles to suggest the best times to fall asleep or wake up, so you wake at the end of a cycle feeling more refreshed.

Why are sleep cycles important?

Waking in the middle of a deep sleep cycle leaves you groggy, while waking at the end of a cycle feels more natural and energising, which is what the calculator aims for.

How many hours of sleep do I need?

Most adults need about seven to nine hours per night, which is roughly five to six full sleep cycles. The calculator helps you plan bedtimes to reach this.