OneFreePlace · Tool #142

Plan enough sleep first. Treat “90-minute cycles” as an estimate.

Build a bedtime or wake-time plan from an age-based sleep target, sleep-onset delay and overnight awake time. Or analyze an existing schedule, then inspect sleep opportunity, estimated sleep, efficiency, cycle uncertainty and seven-night consistency.

✓ CDC age-based sleep references✓ Bedtime & wake-time planner ✓ Sleep opportunity vs estimated sleep✓ 80–100 min cycle uncertainty ✓ Seven-night consistency tracker

Sleep Calculator

duration first · latency · awakenings · cycle range · weekly consistency

Sleep plan

Start with duration, then calculate the clock time.

Age group

Target sleep hours

Clock display

Planner modeClock arithmetic uses local wall-clock time and assumes an ordinary night without a daylight-saving clock change.

Wake time

Time to fall asleep · minutes

Estimated awake time after falling asleep · minutes

Wind-down buffer before bed · minutes

Cycle explorerFor education only—duration and regularity matter more than hitting a theoretical cycle boundary.

Short cycle · minutes

Nominal cycle · minutes

Long cycle · minutes

CDC: adults ages 18–60 should get at least 7 hours of sleep per day. Your selected target is adjustable because individual sleep need varies.

Primary plan

Calculating

—

bedtime

Enter a valid sleep schedule.

Target / estimated sleep—sleep, not just time in bed

Time in bed—includes sleep latency + overnight awake time

Sleep efficiency—estimated sleep ÷ time in bed

Wind-down starts—selected buffer before lights out

Nominal cycle count—using your nominal cycle length

80–100 style cycle range—possible cycle count range, not exact physiology

Duration comes firstCycle timing is approximate; protect enough total sleep and a consistent schedule.

Schedule audit

See the clock arithmetic without hidden assumptions. The planner distinguishes lights-out time, estimated sleep onset, actual sleep target and final wake time.

Age-based sleep reference

The CDC table reports recommended sleep per 24 hours; for younger children, the listed total can include naps.

Cycle uncertainty explorer

NIH describes cycles restarting around every 80–100 minutes. The ranges below show why a single fixed 90-minute bedtime can create false precision.

Cycles	Sleep-duration range	Wake-time planner: bedtime window	Meets selected age minimum?

Why this is not a “magic 90-minute” calculator

Cycles varyNIH describes roughly 80–100 minute cycles and four to six cycles per night. They are not identical stopwatch intervals.

Variable

Falling asleep is not instantThe calculator keeps sleep-onset latency separate from actual sleep duration instead of subtracting a hidden fixed 15 minutes.

Explicit

Night awakenings matterTime awake after sleep onset lowers actual sleep and sleep efficiency even if time in bed looks adequate.

Accounted

Seven-night consistency tracker

Enter actual sleep hours for any nights you know. The tracker compares them with your chosen target and age minimum without pretending a weekly shortfall is a precise biological “sleep debt.”

CDC sleep-duration reference

Age	Recommended daily sleep	Planner note
0–3 months	14–17 h	24-hour total; infant schedules are fragmented
4–12 months	12–16 h	includes naps
1–2 years	11–14 h	includes naps
3–5 years	10–13 h	includes naps
6–12 years	9–12 h	24-hour total
13–17 years	8–10 h	24-hour total
18–60 years	7+ h	individual need may be higher
61–64 years	7–9 h	24-hour total
65+ years	7–8 h	24-hour total

Important limits

Clock time is not sleep qualityA calculator cannot detect sleep apnea, insomnia, restless legs, circadian disorders or fragmented sleep.

Not measured

No daylight-saving correctionWithout a date and timezone, wall-clock arithmetic cannot know whether a night contains a skipped or repeated hour.

Clock only

Persistent sleep problems need evaluationIf you regularly cannot sleep, feel dangerously sleepy, snore/gasp, or remain unrefreshed despite adequate time, speak with a healthcare professional.

Escalate

Good sleep is more than a cycle count.Healthy sleep includes adequate duration, appropriate timing, regularity, good quality and absence of untreated sleep disorders. Use this calculator for schedule planning—not to diagnose sleep problems or promise that a particular alarm minute will make you refreshed.