New — Energy score for every wake-up slot

Sleep smarter. Wake up refreshed.

Find the perfect bedtime or wake-up time using 90-minute sleep cycles. Free, instant, no account required.

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Wake-Up Calculator

If I go to bed now — when should I wake up without feeling groggy?
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Bedtime Calculator

I need to wake at 7 AM — what time should I go to bed?
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Power Nap

20-min nap or full cycle — wake at the right moment.

Sleep guides

Understanding sleep cycles

REM, non-REM, and ideal duration explained simply.

Sleep deprivation

Sleep debt and recovery.

Sleep & productivity

Performance at work and in sports.

Wake up at a set time

Pre-configured bedtime calculator for every common wake-up time. All times →

4:00 AM 4:15 AM 4:30 AM 4:45 AM 5:00 AM 5:15 AM 5:30 AM 5:45 AM 6:00 AM 6:15 AM 6:30 AM 6:45 AM 7:00 AM 7:15 AM 7:30 AM 7:45 AM 8:00 AM 8:15 AM 8:30 AM 8:45 AM 9:00 AM 9:15 AM 9:30 AM 9:45 AM 10:00 AM 10:15 AM 10:30 AM 10:45 AM 11:00 AM 11:15 AM 11:30 AM 11:45 AM 12:00 PM
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100% free, 100% private

All calculations run in your browser. No sleep data is sent to our servers.

  • → Energy score (1–100) for every wake-up slot
  • → Customizable latency and cycle length
  • → Shareable links with your settings

Always free

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Frequently asked questions

How long is a sleep cycle?

About 90 minutes on average, ranging from 80 to 120 minutes. CycleZen uses 90 min by default — fully adjustable.

What is sleep latency?

Time between getting in bed and actually falling asleep. The scientific average is 14 minutes. CycleZen includes this in every calculation.

How does the energy score work?

Waking at the end of a cycle (light sleep) scores higher. Waking during deep sleep scores lower — that groggy feeling is sleep inertia.

Is CycleZen free?

Yes, completely free. The site is funded by Google AdSense ads with your cookie consent.

Is my data private?

Yes. Times you enter stay in your browser. No signup, no server storage of your sleep habits.

What time should I go to bed if I wake at 6 AM?

Use our bedtime calculator or the dedicated 6:00 AM wake page. Typical options: 9:46 PM, 11:16 PM, or 12:46 AM for 4, 5, or 6 full cycles.