In bed at 11 PM, you wake at the end of a fifth 90-minute cycle at 6:45 AM, counting 15 minutes to fall asleep.
General information, not medical advice. Read the disclaimer
| Bedtime | 4 cycles (6 h of sleep) | 5 cycles (7.5 h of sleep) | 6 cycles (9 h of sleep) |
|---|---|---|---|
| 8:00 PM | 2:15 AM | 3:45 AM | 5:15 AM |
| 8:30 PM | 2:45 AM | 4:15 AM | 5:45 AM |
| 9:00 PM | 3:15 AM | 4:45 AM | 6:15 AM |
| 9:30 PM | 3:45 AM | 5:15 AM | 6:45 AM |
| 10:00 PM | 4:15 AM | 5:45 AM | 7:15 AM |
| 10:30 PM | 4:45 AM | 6:15 AM | 7:45 AM |
| 11:00 PM | 5:15 AM | 6:45 AM | 8:15 AM |
| 11:30 PM | 5:45 AM | 7:15 AM | 8:45 AM |
| 12:00 AM | 6:15 AM | 7:45 AM | 9:15 AM |
| 12:30 AM | 6:45 AM | 8:15 AM | 9:45 AM |
| 1:00 AM | 7:15 AM | 8:45 AM | 10:15 AM |
| 1:30 AM | 7:45 AM | 9:15 AM | 10:45 AM |
How it is computed
Wake time = bedtime + 15 minutes to fall asleep + number of cycles × 90 minutes. Four cycles give 6 hours of sleep, five give 7.5 hours and six give 9 hours. Waking between cycles, in light sleep, usually feels easier than waking from deep sleep.
FAQ
Are sleep cycles always 90 minutes?+
No. They range from about 80 to 110 minutes and change across the night; 90 minutes is an average. The calculator lets you change the cycle length.
How many cycles do adults need?+
Most adults need 7 to 9 hours, which is five or six cycles. Four cycles (6 hours) is short for regular use.