Sleep Calculator
Wake up refreshed by aligning with your sleep cycles. Choose whether you're setting a wake time or a bedtime, and we'll suggest times built on 90-minute cycles (plus 15 minutes to fall asleep).
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Check it outWhy 90-minute cycles
Sleep moves through cycles of roughly 90 minutes, ending in light sleep. Waking at the end of a cycle — rather than mid-cycle — tends to feel more refreshing than the same amount of sleep cut off at a deep stage. The suggestions add about 15 minutes to fall asleep, then count whole cycles. Most adults do best on 5–6 cycles (7.5–9 hours).
How it’s calculated
Built on ~90-minute sleep cycles plus ~15 minutes to fall asleep; it suggests waking after 4–6 full cycles (about 6–9 hours).
Results update as you type and are estimates, not professional advice — verify important decisions with a qualified professional.
Worked example
To wake at 7:00 AM, good bedtimes are about 9:45 PM (6 cycles) or 11:15 PM (5 cycles).
Common mistakes
- Treating 90-minute cycles as exact for everyone.
- Forgetting the ~15 minutes it takes to fall asleep.
Where it is used
- Picking a bedtime to wake up refreshed.
- Planning wake times around full sleep cycles.
Frequently asked questions
Are sleep cycles exactly 90 minutes?
It's an average — real cycles range from about 80 to 110 minutes and shift through the night. Treat the times as helpful targets, not guarantees.
How long to fall asleep?
The calculator assumes about 15 minutes. If you usually take longer, shift your bedtime earlier accordingly.
How many cycles should I aim for?
Most adults feel best with 5–6 cycles, which is 7.5–9 hours of sleep.
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