Suggest bedtimes or wake times aligned to ~90 minute sleep cycles. Fully client-side — no account, uploads, or remote storage.
Added Apr 18, 2026 · Updated Apr 21, 2026
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Calculates optimal sleep or wake times based on 90-minute sleep cycles. Each full cycle includes light sleep, deep sleep, and REM sleep. Waking between cycles (rather than during them) typically feels more refreshing.
23:00 + 14 min + 6×90 min = 08:14 AM for 6 full cycles (next day), shown with 12-hour times in the table.
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A typical sleep cycle lasts ~90 minutes and includes light sleep, deep sleep (slow-wave), and REM (rapid eye movement) sleep. Waking at the end of a cycle, when you're in light sleep, tends to feel more natural and less groggy than being woken during deep sleep.
Most adults need 5–6 cycles per night (7.5–9 hours). Teenagers may need 6–8 cycles. Athletes and people recovering from illness often benefit from extra sleep.