Find your ideal bedtime and wake-up time based on 90-minute sleep cycles. Wake up refreshed, not groggy. Backed by AASM and Sleep Foundation guidance.
Good sleep isn't just about how many hours you get — it's about waking at the right point in your sleep cycle. Our sleep calculators use the science of 90-minute cycles to help you time your sleep so you wake up feeling rested, alert, and ready for the day. Free, instant, and private.
Have you ever slept 8 full hours and still woken up exhausted? That's because your alarm interrupted you mid-cycle, during deep sleep. A sleep calculator solves this by timing your sleep around complete 90-minute cycles, so you wake during light sleep — when getting up feels natural and easy.
Whether you have a fixed alarm time and need to know when to go to bed, or you're heading to bed now and want to set the smartest alarm, our calculator gives you cycle-aligned times in seconds. It even accounts for the time it takes you to fall asleep.
| Cycles | Sleep Duration | Best For |
|---|---|---|
| 6 cycles | 9 hours | Teens, recovery, catching up |
| 5 cycles | 7.5 hours | Most adults (ideal) |
| 4 cycles | 6 hours | Minimum for a short night |
| 3 cycles | 4.5 hours | Emergency only — not sustainable |
For personalized times, use our Sleep Calculator.
Yes, completely free with no signup. All calculations run in your browser and no data is stored or transmitted.
90 minutes is a population average; real cycles range from 70 to 120 minutes and vary through the night. The calculator improves your odds of waking during light sleep but can't guarantee a perfect wake. Total sleep duration and consistency matter most.
Yes. The calculator works for any sleep schedule, including daytime sleep for night-shift workers. Just enter your planned sleep or wake time. For chronic shift-work sleep issues, consider consulting a sleep specialist.
Yes. We're planning a nap calculator, jet lag calculator, and a sleep debt tracker. Check back regularly or bookmark this page.
Find your ideal bedtime or wake-up time in seconds. Free, instant, and private.
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