Plan bedtime and wake windows with an adjustable cycle model, sleep-onset buffer, and evidence-aware sleep-duration guidance.
Sleep Architecture Profiles & Presets
Calculation Objective
schedule
Sleep Parameters & Timing Anchors
Configure target time, sleep onset latency, and individual cycle length
Calculates backwards to find optimal times to fall asleep.
min
Average time required to drift into sleep (typically 10–20 min).
90 min
75 min (Fast)90 min (Standard)110 min (Long)
Quick Anchor:
Onset Latency:
stars
Optimal Sleep Cycle Recommendation
A planning model. Sleep cycles vary; total duration and regularity remain central.
Ultradian Synchronized
Recommended Bedtime11:15 PM (23:15)7h 45m in bed (7.5h sleep)
Pure Sleep Duration7.5 Hours5 Complete 90-Minute Cycles
Sleep Latency15 min buffer
Estimated REM~99 min
Deep Slow-Wave~68 min
Inertia StatusMinimal
alarm_on
All Sleep Cycle Options
Compare planning windows. A cycle is an approximation, not a guarantee of how your sleep stages will occur.
9:45 PM(21:45)
6 Cycles Deep Rest
9 hrs pure sleep·9h 15m in bed (9h sleep)
Longer sleep opportunity; individual needs vary.
Light 334mDeep 76mREM 130m
11:15 PM(23:15)
5 Cycles 7.5h Planning Option
7.5 hrs pure sleep·7h 45m in bed (7.5h sleep)
The gold-standard 7.5h sleep cycle for adults, maximizing memory consolidation & energy.
Light 283mDeep 68mREM 99m
12:45 AM(00:45)
4 Cycles Moderate
6 hrs pure sleep·6h 15m in bed (6h sleep)
Shorter sleep opportunity; not a routine recommendation.
Light 227mDeep 54mREM 79m
2:15 AM(02:15)
3 Cycles Short Rest
4.5 hrs pure sleep·4h 45m in bed (4.5h sleep)
Short sleep opportunity; regular restriction can impair alertness and performance.
Light 167mDeep 49mREM 54m
90-Minute Ultradian Cycle TrajectoryCycle boundaries are approximate because real sleep cycles vary.
6C
9:45 PM
9h sleep
5C
11:15 PM
7.5h sleep
4C
12:45 AM
6h sleep
3C
2:15 AM
4.5h sleep
speed
Sleep Duration Guidance
Adult sleep-duration guidance; this is not a diagnosis or measurement of sleep quality.
Planned Sleep Duration Adult target range
Target: 7.5 hrs
7.5 hrs
3 hrs11 hrs
Below adult target (3–7 hrs)
Adult target range (7–9 hrs)
Longer sleep (9–11 hrs)
For healthy adults, the AASM/SRS consensus recommends 7 or more hours regularly. Individual needs vary, and duration alone does not measure sleep quality.
compare_arrows
Sleep Planning Comparison
Compare duration and planning assumptions without treating estimated sleep stages as measured data.
SCENARIO COMPARISON
7.5-hour planning window vs. 9-hour planning window
Longer sleep opportunity can be useful for some people; the calculator does not predict hormone secretion or cognitive performance.
insights
6 Cycles (9.0 Hours) holds key advantagesLeads across 3 key metrics including Pure Sleep Duration (1.5 variance).
Scenario A
5 Cycles (7.5 Hours)
VS
Scenario B
6 Cycles (9.0 Hours)
Pure Sleep DurationPure time spent cycling through NREM and REM stages
7.5 hrs
+1.5(+20.0%)
9 hrsAdvantage
REM Dream & Memory CyclesREM sleep expands primarily in the 5th and 6th cycles of the night
99 min
+31(+31.3%)
130 minAdvantage
Deep Slow-Wave (N3) Physical RepairHigh growth hormone release occurs in the initial 3 deep cycles
68 min
+8(+11.8%)
76 minAdvantage
Morning Grogginess RiskBoth avoid waking in the middle of Stage N3 Slow Wave
Low (Waking at Cycle End)
—
Low (Waking at Cycle End)
Total Required In-Bed WindowIncluding planned latency buffer
7h 45m
+2(+28.6%)
9h 15m
insights
Local Sleep Log & Diary
Record actual sleep patterns securely in your browser via IndexedDB
Private & Local
Logged Nights0
Average SleepNo local records
Storage ModeIndexedDB
Privacy100% Client-Side
functions
Mathematical Model & Sleep Physiology
How ultradian rhythms and sleep onset latency are calculated
FORMULA & STEPSUltradian Sleep Schedule Algorithm
The algorithm takes an anchor time (wake or bedtime), computes integer multiples of the biological 90-minute sleep cycle, factors in sleep latency, and normalizes across 24-hour clock boundaries.
4 StepsSequential Calculation Breakdown
1
Ultradian Sleep Cycle Duration
Sleep cycles are variable. A cycle averages roughly 90 minutes, but real cycles can be shorter or longer and change across the night.
2
Sleep Latency (Time to Fall Asleep)
Sleep onset latency is a user-adjustable planning buffer. It shifts the clock time without claiming that everyone falls asleep in the same interval.
3
24-Hour Modulo Clock Calculation
The clock arithmetic wraps across midnight so the suggested time remains valid on a 24-hour clock.
4
Sleep Inertia Prevention
Cycle timing is only a planning approximation. Sleep cycles vary within and between nights, so total sleep duration, regularity and sleep quality matter more than hitting an exact 90-minute boundary.
Clinical principle: Sleep quality is driven as much by cycle completeness as total hours.
Calculator guide
How to use the Sleep Calculator
Find suggested bedtimes or wake times using adjustable sleep-cycle timing and sleep onset.
01Set inputsChoose values, units and assumptions.
→
02Apply the modelPlanned time = target time ± (cycles × cycle length + sleep onset).
→
03Read the resultCheck the output against the assumptions before using it.
menu_book
What this calculator does
The planner works backward from a desired wake time or forward from a desired bedtime and lets the user adjust cycle length and sleep onset.
functions
Formula & method
Planned time = target time ± (cycles × cycle length + sleep onset).
fact_check
Assumptions & notes
Sleep cycles vary between people and across the night.
