Sleep cycle calculator
Time your bedtime or alarm to line up with the end of a sleep cycle, so you're more likely to wake up feeling rested rather than mid-cycle.
Fill in the fields and press Calculate to see your result here.
How this calculation works
A full sleep cycle — moving through light sleep, deep sleep and REM — lasts roughly 90 minutes. Waking up at the end of a cycle, rather than in the middle of one, is widely reported to feel less groggy. This calculator counts back (or forward) in 90-minute blocks from your target time, adding your estimated time to fall asleep, and shows a few options covering 5 or 6 full cycles (roughly 7.5–9 hours) down to a shorter nap-length rest.
Health note: Sleep needs vary from person to person. This tool gives general guidance and is not medical advice. If you have ongoing sleep problems, speak with a doctor.
Tips
This is a general pattern, not an exact science
Individual sleep-cycle length varies (typically 70–120 minutes) and shifts through the night, so treat the times shown as good starting points to experiment with rather than an exact formula.
Most adults do best with 4–6 full cycles
That works out to roughly 6–9 hours of actual sleep time, before adding the minutes it takes you to fall asleep.
Allow time to fall asleep
The default is 15 minutes. Change it if you usually drift off faster or slower.
Regularity beats precision
Going to bed and waking at similar times each day often helps more than hitting an exact cycle boundary.
Talk to a doctor about persistent problems
If you often feel unrested despite enough time in bed, a health professional can look for causes.
Frequently asked questions
Why 90 minutes specifically?
It's the commonly cited average length of one full sleep cycle in adults, though it can range from about 70 to 120 minutes from person to person and night to night.
Is this a substitute for tracking my actual sleep?
No — a sleep tracker or professional sleep study measures your real cycles. This calculator applies a population average, which is a reasonable planning tool but won't be exact for everyone.