To wake up at 6:30 AM, try falling asleep at
Best match
10:45 PM
5 cycles · 7h 30m of sleep
Other options
- 9:15 PM Ideal 6 cycles · 9h of sleep
- 12:15 AM Okay 4 cycles · 6h of sleep
Why: each cycle is about 90 minutes and we allow 15 minutes to fall asleep, so the alarm lands between cycles. Aim for 5–6 cycles (7.5–9 hours) if you can.
Questions about sleep cycles
How does the sleep calculator work?
Sleep moves in cycles of roughly 90 minutes. We count backwards from your wake-up time in whole cycles and add the time it takes you to fall asleep, so your alarm lands at the end of a cycle, when sleep is lightest.
How many sleep cycles do I need?
Most adults feel best after 5–6 cycles, which is 7.5–9 hours. Four cycles (6 hours) is a bare minimum you should not rely on every night.
Why does it add 15 minutes?
The average person takes around 15 minutes to fall asleep. Open "Fine-tune for you" to change this if you drop off faster or slower.
Is a 90-minute cycle accurate for everyone?
It is an average. Real cycles range from about 80 to 110 minutes and change through the night, so treat the results as a good starting point and adjust the cycle length to what works for you.
Does this replace medical advice?
No. If you regularly feel unrested, snore heavily or struggle to sleep, speak to a doctor.
Guides for this tool
General information only. This tool gives general sleep information and is not a substitute for medical advice. If you're worried about your sleep or your child's, talk to a doctor or pediatrician.