Explore possible bedtimes or wake times from a repeating interval, or pick a sleep length and get a single bedtime or alarm. Times wrap past midnight and, in the cycle tab, include an entered fall-asleep delay.
How much sleep by age
CDC sleep-duration guidance by age, per 24 hours (naps included where noted):
| Age group | Recommended sleep |
|---|---|
| 0–3 months | 14–17 hours |
| 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 per night |
| 61–64 years | 7–9 hours |
| 65 years and older | 7–8 hours |
Sleep duration and timing
Sleep stages recur during the night, but their timing is not a fixed repeating clock. The interval mode therefore generates scenarios from the number you enter; it does not detect a person's REM or non-REM stages. Total duration, schedule, health, environment, and sleep continuity can all affect how rested a person feels.
Examples
Wake at 6:00 AM (90-minute cycles, 15 minutes to fall asleep)
Five cycles back from 6:00 AM is 10:15 PM; six cycles is 8:45 PM. Those two are highlighted examples. The rest of the list is 7:15 PM, 11:45 PM, 1:15 AM, 2:45 AM, and 4:15 AM.
Go to bed at 11:00 PM (100-minute cycles, 20 minutes to fall asleep)
Five cycles forward is 7:40 AM; six is 9:20 AM. Then 11:00 AM, 6:00 AM, 4:20 AM, 2:40 AM, and 1:00 AM.
Sleep length of 7 hours 30 minutes before a 6:00 AM wake
Subtract 7 hours 30 minutes from 6:00 AM to get a bedtime of 10:30 PM. Going to bed at 11:00 PM and sleeping 8 hours 15 minutes lands a wake time of 7:15 AM.
Formula
Sleep-cycle times count whole cycles on a 24-hour clock (1,440 minutes). The active target is a wake time or a bedtime:
bedtime = wakeTime − fallAsleep − n × cycleLength
wakeTime = bedtime + fallAsleep + n × cycleLength
n runs from 1 to 7. Results are shown in the order 5, 6 (planning examples), then 7, 4, 3, 2, 1, each wrapped with mod 1,440. Defaults are a 90-minute cycle and 15 minutes to fall asleep.
Sleep length is the same clock arithmetic without cycles:
bedtime = wakeTime − duration
wakeTime = bedtime + duration
Cycle length is an editable planning interval, not a prediction of sleep stage. Treat the highlighted 5- and 6-cycle times as examples, not exact alarms or personalized sleep recommendations.
Sleep-model limits
The cycle list is clock arithmetic using an editable interval and fall-asleep delay. Human sleep cycles vary across a night and between people, so landing on a calculated boundary does not guarantee easier waking or better sleep. The highlighted five- and six-cycle rows are planning examples rather than recommendations. Use the separate duration mode to plan around age-appropriate total sleep; persistent sleep problems need clinical assessment. The American Academy of Sleep Medicine publishes consensus sleep-duration guidance.