Sleep Cycle & Wake Time Calculator
Calculate optimal sleep times and wake times based on 90-minute sleep cycles. Wake at the end of a cycle, not in the middle, to feel rested.
Sleep Cycle Guide
How Sleep Cycles Work
Each sleep cycle is approximately 90 minutes — varies 80-110 minutes between people. Within each cycle: NREM Stage 1 (5-10 min): light dozing, easy to wake. NREM Stage 2 (10-25 min): light sleep, body temperature drops, heart rate slows. NREM Stage 3 (20-40 min): deep sleep, critical for physical recovery, growth hormone release. Hard to wake. REM sleep (10-60 min, longer later in night): dreams, memory consolidation, brain activity high. Waking during deep sleep (Stage 3) feels grim — disorient
Calculating Optimal Wake Time
Method: add 90 minutes × number of cycles + 15 minutes (typical time to fall asleep) to your bedtime. Example bedtime 22:30: 1 cycle (90 min): wake 0:15. 2 cycles: 1:45. 3 cycles: 3:15. 4 cycles: 4:45. 5 cycles: 6:15. 6 cycles: 7:45. For most adults, 5-6 cycles (7.5-9 hours) is optimal. Personalising: cycles vary 80-110 min individually. If you consistently feel groggy at 6:15, try 6:00 or 6:30. Adjust over a few weeks until you find your natural cycle length. Sleep tracking apps (Sleep Cycle, A
Sleep Requirements by Age
National Sleep Foundation recommendations: newborns 0-3 months: 14-17 hours/day. Infants 4-11 months: 12-15 hours. Toddlers 1-2 years: 11-14 hours. Preschoolers 3-5: 10-13 hours. School age 6-13: 9-11 hours. Teens 14-17: 8-10 hours. Young adults 18-25: 7-9 hours. Adults 26-64: 7-9 hours. Older adults 65+: 7-8 hours. Variation: some people genuinely need less (true 'short sleepers' — about 1-3% of population, genetic). More than 1% claim it. Most need 7-9 hours despite saying they don't. Sleep de
Improving Sleep Quality
Sleep hygiene: consistent sleep/wake times — even at weekends. Bedroom 16-19°C ideal. Dark, quiet. No screens 1 hour before bed (blue light suppresses melatonin). No caffeine after midday (half-life 5-6 hours — afternoon coffee affects sleep). No alcohol within 3 hours of bed (impairs deep sleep). Daytime: morning sunlight exposure within 1 hour of waking. Exercise improves sleep but not within 2 hours of bedtime. Limit naps to 20-30 minutes (otherwise enter deep sleep, disorienting wake). Or fu
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