Math
Sleep Calculator
A sleep cycle = 90 minutes. The tool finds the wake times that will suit you best.
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sleep cycles
(includes ~14 min to fall asleep)
Select a time to calculate
What does Sleep Calculator?
The sleep calculator finds optimal wake-up (or bedtime) hours based on 90-minute sleep cycles.
How to use Sleep Calculator?
- Choose a mode: "I want to wake up at" or "I'm going to sleep at".
- Enter the desired time.
- The tool shows 4–6 recommended times based on complete sleep cycles.
Key features
- Calculation based on 90-minute sleep cycles
- Includes average 14 minutes to fall asleep
- Works both ways — from wake time or from bedtime
Frequently asked questions
What is a sleep cycle?
A sleep cycle is a sequence of sleep stages lasting about 90 minutes. It's best to wake up at the end of a cycle rather than in the middle.
How many sleep cycles are recommended?
Most adults need 4–6 cycles (6–9 hours of sleep) per night.
Is this tool free?
Yes, this tool is completely free and requires no registration.
Is my data saved?
No. All calculations happen in your browser only — no data is sent to any server.