Sleep Calculator
Find the best time to go to sleep or wake up based on natural 90-minute sleep cycles.
You should go to sleep at one of these times:
How the Sleep Calculator Works
Sleep is not a single continuous state — it happens in cycles. Each full sleep cycle lasts about 90 minutes and moves through light sleep, deep sleep, and REM sleep. Waking up at the end of a cycle (rather than in the middle of one) usually leaves you feeling more refreshed.
The average person takes around 15 minutes to fall asleep. This calculator accounts for that, then works backwards (or forwards) in 90-minute blocks to find the best times.
How to Use the Results
- 6 cycles (9 hours): Ideal for most adults, especially if you are active or recovering.
- 5 cycles (7.5 hours): The most commonly recommended amount.
- 4 cycles (6 hours): The minimum for most healthy adults.
- 3 cycles (4.5 hours): Short sleep — not recommended as a regular habit.
Educational Tool Only
This calculator provides general estimates for educational purposes. It is not medical advice. If you experience ongoing sleep problems, please consult a qualified healthcare professional.