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Sleep Calculator

New

Sleep calculator — best wake up time based on sleep cycles

Go to sleep at…

01:15 PM
6 sleep cycles
9.0 hours · Ideal
02:45 PM
5 sleep cycles
7.5 hours · Good
04:15 PM
4 sleep cycles
6.0 hours · Minimum

💡 Sleep happens in 90-minute cycles (light → deep → REM). Waking at the end of a cycle feels much better.

⏰ These times include ~15 minutes to fall asleep.

🌙 NREM 1
Drowsy
😴 NREM 2
Light sleep
💤 NREM 3
Deep sleep
🌀 REM
Dream sleep
Browser-based, files never uploaded Instant results Works on any device

How to use Sleep Calculator

  1. 1Enter your bedtime (or target wake-up time)
  2. 2See optimal wake-up times based on sleep cycles
  3. 3Choose a time that completes full 90-min cycles
  4. 4Aim to wake up between REM cycles to feel refreshed

About this tool

Calculate the best time to wake up or go to sleep based on 90-minute sleep cycles. Avoid waking mid-cycle to feel refreshed. REM sleep cycle optimiser.

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Frequently asked questions

How long is a sleep cycle?

One sleep cycle is approximately 90 minutes. Adults need 5–6 complete cycles (7.5–9 hours).

Why do I feel groggy even after 8 hours?

You may have woken mid-cycle. Try adjusting bedtime by 15 minutes to complete full cycles.