How it works
Sleep runs in cycles of about 90 minutes, from light sleep to deep sleep and REM. Waking at the end of a cycle usually feels easier than being pulled out of deep sleep. The calculator adds the time you take to fall asleep (15 minutes by default) and counts 4 to 6 cycles.
Example
To wake up at 6:30, go to bed at 22:45 (10:45 pm) for 5 cycles (7.5 hours), or at 21:15 for 6 cycles (9 hours).
How much sleep do adults need?
Sleep experts recommend 7 to 9 hours a night for adults, more for teenagers and children. Regular times every day, including weekends, help as much as the total.
Frequently asked questions
Is every sleep cycle exactly 90 minutes?
No. Cycles last about 80 to 110 minutes and change during the night, so use the result as a guide and adjust to how you feel.
What if I wake up tired anyway?
Ongoing tiredness, loud snoring or pauses in breathing are worth discussing with a doctor.
See also
Results are estimates for information only and are not financial, legal or medical advice. Rates, taxes and fees vary — confirm with a professional or your lender.