Everyday utility
Find bedtime or wake-up times from cycle count, sleep latency, and a 90-minute cycle planning assumption.
When to use this
It is useful before early shifts, school mornings, flights, race days, routine resets, or nights when you want several no-math bedtime options.
Default result
For a 7:00 AM wake-up, 15-minute latency, and 5 cycles, the server-rendered bedtime is 11:15 PM.
Cycle options
Wake at 7:00 AM with 15 minutes to fall asleep.
| Option | Time | Sleep | In bed | Note |
|---|---|---|---|---|
| 6 cycles | 9:45 PM | 9h | 9h 15m | Adult-friendly range for many people if sleep quality is good. |
| 5 cycles | 11:15 PM | 7h 30m | 7h 45m | Adult-friendly range for many people if sleep quality is good. |
| 4 cycles | 12:45 AM | 6h | 6h 15m | Short night; use only when a full night is not possible. |
| 3 cycles | 2:15 AM | 4h 30m | 4h 45m | Very short night; not a routine target. |
The default example uses wake-up mode, a 7:00 AM target wake time, 15 minutes to fall asleep, and a 90-minute cycle length.
For 5 cycles, sleep time is 5 x 90 = 450 minutes, or 7h 30m.
Time in bed is 450 + 15 = 465 minutes, or 7h 45m.
Bedtime is 7:00 AM - 7h 45m = 11:15 PM.
The other options are 9:45 PM for 6 cycles, 12:45 AM for 4 cycles, and 2:15 AM for 3 cycles.
In wake-up mode, bedtime = wake time - sleep latency - (cycles x cycle length). In bedtime mode, wake time = bedtime + sleep latency + (cycles x cycle length).
With the default 15-minute latency and 90-minute cycles, 5 cycles points to 11:15 PM and 6 cycles points to 9:45 PM.
Five 90-minute cycles equal 7h 30m of sleep. Six cycles equal 9h. Those are planning options, not personal medical requirements.
Cycle length varies, sleep latency varies, and sleep quality can be disrupted by stress, alcohol, illness, medications, noise, caregiving, shift work, and sleep disorders.
Enter the required wake time, compare the 5 and 6-cycle options, then set a wind-down alarm before the bedtime you want to protect.
Use the copy button to save the preferred option, cycle count, sleep duration, and latency assumption.
| Reference point | Value | Source | Date | Verification note |
|---|---|---|---|---|
| Sleep-cycle assumption | 90 minutes per cycle, editable from 70 to 120 minutes | L-SeqSleepNet paper on sleep-cycle sequence modelling | As of June 19, 2026; arXiv version published January 2023 | The source describes human sleep as cyclical with an approximately 90-minute period. Individual cycle timing varies. |
| Adult sleep-duration reference | Adults should sleep 7 or more hours on a regular basis | AASM and Sleep Research Society consensus statement | As of June 19, 2026; consensus statement published June 2015 | This calculator is not medical advice and does not diagnose insomnia, sleep apnea, circadian rhythm disorders, or fatigue. |
It estimates bedtime or wake-up times by adding or subtracting sleep cycles and your estimated time to fall asleep.
NREM and REM sleep move in cycles, and 90 minutes is a common planning approximation. The input is editable because real cycles vary by person and night.
No. Sleep quality, total sleep time, circadian timing, stress, alcohol, illness, medications, and sleep disorders can matter more than cycle math.
Five 90-minute cycles give about 7.5 hours of sleep, and six cycles give about 9 hours. Many adults use that range as a planning starting point.
No. Persistent insomnia, loud snoring, breathing pauses, severe daytime sleepiness, or safety concerns should be discussed with a qualified clinician.
Yes, but short naps work differently than full-night sleep. Use the custom cycle and latency inputs for experiments, not as a medical sleep plan.
Decision path
Use the date calculator to count how many nights are left before an event, trip, race, or schedule change.
Wind-downIf bedtime slips because of screens, compare a small daily cut with reclaimed time.
RoutinePlace a sleep routine inside a week-grid if the goal is part of a broader reset.
