Sleep happens in ~90-minute cycles — waking between cycles leaves you refreshed. Tell us when you must wake up, and we'll show the best bedtimes. Or enter your bedtime to see ideal wake-up times.
Human sleep runs in roughly 90-minute cycles of light, deep and REM sleep. Waking at the end of a cycle — not in deep sleep — feels much better.
Most adults need 7–9 hours per night (about 5–6 full cycles). Teenagers need 8–10 hours.
It takes most people about 15 minutes to fall asleep, so the calculator adds that buffer to the cycle math.
No. ToolKishop's sleep calculator is informational only. For sleep problems, please see a qualified health professional.
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