Sleep Calculator
Find optimal sleep and wake times based on 90-minute sleep cycles
You fall asleep in about 14 minutes
Recommended Times
How to Use
- Select your calculation mode: wake-up time or bedtime.
- Enter the time you want to wake up or go to sleep.
- Click 'Calculate' to see the recommended sleep or wake times.
- Times are calculated based on 90-minute sleep cycles.
- The calculator accounts for approximately 14 minutes to fall asleep.
About Sleep Cycles
Sleep Cycle Basics
A complete sleep cycle lasts approximately 90 minutes and consists of four stages: three NREM (non-REM) stages and one REM stage. NREM Stage 1 is light sleep lasting 5–10 minutes. NREM Stage 2 consolidates memory. NREM Stage 3 is deep restorative sleep. REM sleep involves dreaming and emotional processing. A full night includes 4–6 complete cycles.
Why Cycles Matter
Waking up at the end of a cycle (light sleep stage) leaves you feeling refreshed. Waking in the middle of a deep sleep cycle causes sleep inertia — that groggy, disoriented feeling. Timing your alarm to align with the end of a 90-minute cycle can dramatically improve how you feel in the morning, even with less total sleep.
Optimal Sleep Duration
Adults need 7–9 hours of sleep per night (4–6 full cycles). Teenagers need 8–10 hours. School-age children need 9–11 hours. Consistent sleep deprivation impairs cognitive function, immune response, emotional regulation, and metabolism. Even one night of poor sleep can reduce alertness and performance by 20–30%.
Sleep Hygiene Tips
Maintain a consistent sleep schedule even on weekends. Keep your bedroom cool (18–20°C), dark, and quiet. Avoid screens (phones, TV) 1 hour before bed — blue light suppresses melatonin. Avoid caffeine after 2 pm. Regular exercise improves sleep quality but avoid vigorous exercise within 2 hours of bedtime.
Key Features
- Calculates optimal times based on 90-minute sleep cycles
- Accounts for 14-minute average time to fall asleep
- Shows multiple options with cycle count for each
- Two modes: wake-up time or bedtime calculation