Sleep cycle calculator
Sleep runs in cycles of roughly 90 minutes. Waking at the end of one feels better than waking in deep sleep, even after less total sleep.
minutes
minutes
Time to allow in bed
7:44:00
- Actual sleep
- 7.50 hours
- Total minutes in bed
- 464
- Four cycles instead
- 6:14:00
- Six cycles instead
- 9:14:00
- Hours short of eight
- 0.50
Show the working
- Cycle length = 90
- Cycles wanted = 5
- Time to fall asleep = 14
- sleep_minutes = 5 * 90 = 450
- Total minutes in bed = 450 + 14 = 464
- Time to allow in bed = 464 * 60 = 27 840
- Actual sleep = 450 / 60 = 7.5
- Four cycles instead = (4 * 90 + 14) * 60 = 22 440
- Six cycles instead = (6 * 90 + 14) * 60 = 33 240
- Hours short of eight = 8 - 7.5 = 0.5
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- time in bed = cycles x cycle length + time to fall asleep
Ninety minutes is an average. Real cycles run from 70 to 120 minutes and lengthen through the night.
Total sleep matters more than cycle alignment. Do not trade an hour of sleep for a tidier number of cycles.