Sleep Cycle Calculator
Find the best time to fall asleep so you wake up between sleep cycles — and feel more refreshed.
Recommended bedtimes
Based on 90-minute sleep cycles.
General guidance only — not medical advice.
How this sleep calculator works
The calculator works backward from your chosen wake-up time. It subtracts several complete 90-minute sleep cycles and adds an estimated 15 minutes for falling asleep.
Waking between cycles may feel easier than waking during deeper sleep. The first option gives the longest rest, while the shorter options can be useful when bedtime is limited.
Sleep cycle formula
Recommended bedtime: wake-up time − (number of cycles × 90 minutes) − 15 minutes
Example: for a 7:00 AM wake-up time and 6 cycles, the suggested bedtime is about 9:45 PM.
How to choose a bedtime
Most adults do best with a consistent schedule. Choose a bedtime you can repeat, reduce screen exposure before bed, and avoid late caffeine if sleep quality is a problem.
FAQ
How long is one sleep cycle?
On average, a sleep cycle is around 90 minutes, though it varies by person and night.
How many sleep cycles do I need?
Many people feel best with 4–6 cycles (about 6–9 hours). Try a few options and see what works for you.
Why do I wake up tired even after many hours?
If you wake during deep sleep, you may feel groggy. Timing your wake-up between cycles can help.
What if I work night shifts?
You can still use the calculator — just enter the time you plan to wake up.
Is this medically accurate?
It's a general guideline based on average cycle length and fall-asleep time. For medical concerns, consult a professional.
Sleep habits that make the result more useful
Use the calculator as a planning tool, then keep the same wake-up time for several days. A stable wake-up time helps your body clock settle, which can make falling asleep easier at night.
For better sleep quality, try to keep the last hour before bed simple: dim lights, avoid heavy meals, reduce screens, and keep caffeine earlier in the day. If you regularly struggle with insomnia, loud snoring, or daytime sleepiness, this calculator should not replace medical advice.