What time do you want to wake up?

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Minute

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If you want to go to bed now...

Bedtime

Note: The average person takes about 15 minutes to fall asleep. A good night’s sleep consists of 5–6 complete 90-minute cycles. Waking up at the end of a cycle helps you feel more refreshed.

How This Sleep Calculator Works

This free Sleep Calculator uses the science of 90-minute sleep cycles to recommend the best times to go to bed or wake up. Instead of just counting total hours, it helps you wake up at the end of a natural sleep cycle so you feel more refreshed and less groggy.

Why 90-Minute Sleep Cycles?

During sleep, your body moves through repeating cycles of light sleep, deep sleep, and REM sleep. Each full cycle lasts approximately 90 minutes. Waking up in the middle of a cycle (especially during deep sleep) often causes that heavy, tired feeling.

By timing your sleep to complete full cycles, you increase the chance of waking up during a lighter stage of sleep — which feels much better.

How to Use the Calculator

Know your wake-up time? → Select the time and click “Calculate bedtime”. You’ll get 6 suggested bedtimes.
Going to bed now? → Click “Calculate wake-up time”. You’ll see the best times to set your alarm.
The first two results are marked as Suggested because they give you 5–6 full cycles (ideal for most adults).

15 Minutes to Fall Asleep

The calculator automatically adds 15 minutes — the average time it takes most people to fall asleep. This makes the recommendations more realistic and accurate.

Frequently Asked Questions

Most adults need 7–9 hours of sleep. This usually equals 5 to 6 full 90-minute cycles. The calculator shows options for different cycle counts so you can choose what fits your schedule.

Even if you sleep 8 hours, you may be waking up in the middle of a sleep cycle. Using this calculator helps you wake up at the end of a cycle, which often reduces that groggy feeling.

Yes. Sleep researchers have observed that human sleep naturally organizes into cycles of roughly 90 minutes. While individual cycle length can vary slightly (80–120 minutes), 90 minutes is the widely accepted average used by most sleep calculators.

Yes. For a short power nap, aim for 1 cycle (about 90 minutes) or a very short 20–25 minute nap. Longer naps of 2–3 cycles can also be planned using the same method.

The 90-minute model works well for most healthy adults. Teenagers, older adults, or people with sleep disorders may have different needs. Use the calculator as a helpful guide and adjust based on how you feel.