8 min read
2026-01-20
Sleep consists of repeating cycles lasting 90 minutes. Each cycle includes several phases:
| Phase | Duration | Description |
|---|---|---|
| N1 (falling asleep) | 5-10 min | Transition from wakefulness to sleep |
| N2 (light sleep) | 20-25 min | Decreased body temperature, slowed heart rate |
| N3 (deep sleep) | 20-40 min | Tissue restoration, strengthening immunity |
| REM (rapid eye movement sleep) | 10-20 min | Dreaming, information processing |
| Age | Recommended time |
|---|---|
| 6-13 years | 9-11 o'clock |
| 14-17 years | 8-10 hours |
| 18-64 years | 7-9 hours |
| 65+ years | 7-8 hours |
The calculator calculates the optimal time to fall asleep or wake up based on 90-minute cycles. Waking up at the end of the cycle (in the light sleep phase) gives a feeling of vigor.
You need to get up at 7:00 - the optimal time to fall asleep:
5 cycles: 23:30 (7.5 hours of sleep)
6 cycles: 22:00 (9 hours of sleep)
Add 15 minutes to fall asleep
Temperature in the bedroom (optimally 18-20°C)
No blue light an hour before bed
Regular sleep and wake-up routine
Caffeine - no later than 6 hours before bedtime
See also: Water norm calculator, Heart rate zones, Calorie calculator