Find bedtimes and wake-up times that fit 90-minute sleep cycles so you wake up refreshed.
Count back whole 90-minute sleep cycles from your wake-up time, plus about 15 minutes to fall asleep. To wake at 6:30 AM, go to bed at 10:45 PM (5 cycles) or 9:15 PM (6 cycles).
Sleep moves through repeating cycles of lighter, deeper and REM sleep that average about 90 minutes. Waking at the end of a cycle, rather than in the middle of deep sleep, often feels easier. This calculator takes the time you want to wake up (or go to bed), allows for the time it takes you to fall asleep, and lists the bedtimes or wake-up times that line up with complete cycles.
A second tool works out bedtime or wake time for a set number of hours of sleep. Cycle length varies from person to person, so you can adjust it. This is a planning aid and not medical advice; persistent sleep problems should be discussed with a doctor. To measure hours between two times, use the Hours Calculator.
The calculator works in minutes around the clock.
| Sleep cycles | Sleep time | Go to bed at |
|---|---|---|
| 7 cycles | 10.5 h | 19:45 (7:45 PM) |
| 6 cycles | 9 h | 21:15 (9:15 PM) |
| 5 cycles | 7.5 h | 22:45 (10:45 PM) |
| 4 cycles | 6 h | 00:15 (12:15 AM) |
| 3 cycles | 4.5 h | 01:45 (1:45 AM) |
Needs vary with age and the individual. The US CDC recommends the following amounts.
| Age group | Recommended sleep |
|---|---|
| 0–3 months | 14–17 hours per day |
| 4–12 months | 12–16 hours (including naps) |
| 1–2 years | 11–14 hours (including naps) |
| 3–5 years | 10–13 hours (including naps) |
| 6–12 years | 9–12 hours |
| 13–18 years | 8–10 hours |
| 18–60 years | 7 or more hours |
| 61–64 years | 7–9 hours |
| 65 years and older | 7–8 hours |
A sleep cycle is one pass through the stages of non-REM and REM sleep. It lasts about 90 minutes on average, and a night usually has four to six.
Choose “I want to wake up at” and enter the time to see bedtimes, or choose “I want to go to bed at” to see wake-up times.
90 minutes is the commonly cited average cycle length, but it ranges from about 70 to 120 minutes between people and through the night. You can change it in the calculator.
Most people take 10–20 minutes. The calculator uses 15 by default — change it if you fall asleep faster or slower.
Most adults need 7 or more hours; 5 cycles (7.5 hours) or 6 cycles (9 hours) are good targets.
Many people find it easier to wake from lighter sleep, but the evidence for exact timing is limited. Getting enough total sleep and a regular schedule matters more.
The calculator shows 3-cycle (4.5 hours) options too, but regularly sleeping this little is not recommended.
A short nap of 20 minutes, or a full 90-minute cycle, avoids waking from deep sleep. Use the Sleep Length calculator for exact durations.
No. It is a planning tool. See a doctor if you have trouble sleeping or feel tired despite enough hours.
No. Everything runs in your browser.
