justyourcalculatorSleep Calculator
Wake up between sleep cycles, not in the middle of one.
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Sleep Calculator
Best bedtime or wake-up time by sleep cycles
Go to bed at
9:45 PM or 11:15 PM
For 6 or 5 full cycles (9 or 7.5 hours of sleep), waking at 7:00 AM
- 6 cycles (9 h sleep)
- 9:45 PM
- 5 cycles (7.5 h sleep)
- 11:15 PM
- 4 cycles (6 h sleep)
- 12:45 AM
- 3 cycles (4.5 h sleep)
- 2:15 AM
Assumes 90-minute cycles and 15 minutes to fall asleep. Real cycles vary from about 70 to 120 minutes.
| Age | Sleep per day |
|---|---|
| Newborn (0-3 months) | 14-17 hours |
| Infant (4-11 months) | 12-15 hours |
| Toddler (1-2 years) | 11-14 hours |
| Preschool (3-5 years) | 10-13 hours |
| School age (6-13 years) | 9-11 hours |
| Teen (14-17 years) | 8-10 hours |
| Young adult (18-25 years) | 7-9 hours |
| Adult (26-64 years) | 7-9 hours |
| Older adult (65+ years) | 7-8 hours |
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How the sleep calculator works
Sleep runs in cycles of roughly 90 minutes, from light sleep to deep sleep to REM. Waking at the end of a cycle usually feels easier than waking in deep sleep.
The calculator counts back (or forward) in 90-minute steps from your time, adding the time it takes you to fall asleep. Most adults need 5 or 6 cycles, which is 7.5 to 9 hours.
Using and checking your result
Published by JustYourCalculator. Check the units and assumptions above, and compare a known example before relying on the output. Calculations use browser arithmetic and may round displayed values.
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