Utilz
Sleep Calculator
Find the best time to sleep or wake up
Recommended Times
21:45
6 cycles · 9h
23:15
5 cycles · 7.5h
00:45
4 cycles · 6h
Includes 15 minutes to fall asleep
Sleep Science
Each sleep cycle (~90 min) includes light sleep, deep sleep, and REM stages.
Adults need 7-9 hours (5-6 cycles) for optimal health.
Tip: Keep a consistent sleep schedule, even on weekends.
Why Use This Tool?
- Waking between sleep cycles reduces grogginess.
- Calculates optimal times based on 90-minute sleep cycles.
- Accounts for the average 15-minute time to fall asleep.
How It Works
Each sleep cycle lasts about 90 minutes. 6 cycles = 9 hours (ideal), 5 cycles = 7.5 hours (good), 4 cycles = 6 hours (minimum). The calculator adds 15 minutes to account for falling asleep.
How to Use
- Choose mode: wake-up time or bedtime
- Enter the time
- View recommended sleep/wake times based on complete cycles
FAQ
How many hours of sleep do I need?
Most adults need 7-9 hours (5-6 sleep cycles). 6 cycles (9 hours) is ideal, 5 cycles (7.5 hours) is good, and 4 cycles (6 hours) is the minimum recommended.
Why 90-minute cycles?
Sleep occurs in 90-minute cycles of light sleep, deep sleep, and REM. Waking at the end of a cycle (during light sleep) helps you feel refreshed rather than groggy.
Does it take 15 minutes to fall asleep?
On average, yes. If you know you fall asleep faster or slower, mentally adjust the times accordingly.