Bedtime calculator
Tell this bedtime calculator when you must wake up and it returns the bedtimes that put you at the end of a sleep cycle — not the middle of one. The default model is five 90-minute cycles plus 15 minutes to fall asleep; both numbers are adjustable, because your cycle length is yours, not the internet's. Flip the direction to start from bedtime instead.
90 min is the average — yours may differ.
10–20 min is typical for a healthy sleeper.
Go to bed at one of these times
the arithmetic · 5 cycles × 90 min + 15 m to fall asleep = 7 h 45 m in bed → in bed by 10:45 pm to wake at 6:30 am
Waking at the end of a cycle — rather than mid-cycle in deep sleep — is what makes an alarm feel bearable. The highlighted option gives most adults enough total sleep; pick a longer one if you're repaying debt.
Planning tool, not medical advice. These figures are population averages for scheduling your sleep — they don't diagnose or treat any condition. See a clinician for persistent sleep problems.
How does the bedtime calculator work?
Sleep is organised into cycles of roughly 90 minutes, each passing from light sleep into deep slow-wave sleep and then REM. Waking at the boundary between cycles is noticeably easier than waking from deep sleep mid-cycle, which is the mechanism behind every "sleep cycle alarm". So the calculation is deliberately simple:
bedtime = wake time − (cycles × cycle length) − sleep latency
For a 6:30 am wake with 5 cycles of 90 minutes and a 15-minute latency: 6:30 − 7 h 30 m − 0:15 = 10:45 pm. The timeline above draws exactly that arithmetic — band for sleep, a lighter lead-in for the latency, ticks at each cycle boundary.
Why does time to fall asleep change the answer?
Sleep latency — the gap between lights-out and actual sleep — averages 10–20 minutes in healthy adults. Most bedtime calculators silently assume zero, which means every bedtime they show is ~15 minutes too late: you are still awake when your first cycle was meant to start. Set yours honestly; if you regularly take more than 30 minutes to fall asleep, that itself is worth mentioning to a clinician.
How many cycles do you need?
Five cycles (7.5 hours of sleep) suits most adults and is the option to default to. Six cycles is the tool for repaying sleep debt or hard training blocks. Four cycles is a damage-limitation night, not a schedule. Whatever the count, keep the wake time fixed and let the bedtime move — a steady wake time is the single strongest anchor for your circadian rhythm.
FAQ
What time should I go to bed if I wake up at 7 am?
With 90-minute cycles and 15 minutes to fall asleep: 11:15 pm for 5 cycles (7 h 30 m asleep), 9:45 pm for 6 cycles, or 12:45 am for 4 cycles. The 5-cycle bedtime is the right answer for most adults; use 6 if you are repaying sleep debt.
Why does the calculator add time to fall asleep?
Because the cycles count actual sleep, and you do not fall asleep the instant your head hits the pillow. Healthy sleep latency is 10–20 minutes; the calculator defaults to 15 and adds it on top of the cycles. A tool that ignores latency hands you a bedtime that is ~15 minutes too late every night.
Is it bad to wake up in the middle of a sleep cycle?
It is not harmful, but it feels worse. Waking from deep slow-wave sleep (which concentrates in the first half of the night) produces sleep inertia — that groggy, drugged feeling that can linger 20–30 minutes. Waking at a cycle boundary, when sleep is light, makes the same amount of sleep feel markedly more refreshing.
How is this different from a sleep cycle calculator?
Same engine, different door: this page starts from your wake time and returns bedtimes; the sleep cycle calculator starts from bedtime and returns alarms, and goes deeper on the cycle model itself. Your settings carry over between them.
How we source this
The sleep-duration figures come from the National Sleep Foundation's 2015 consensus panel (Hirshkowitz et al., Sleep Health) — 18 experts convened from 12 stakeholder organisations, reviewing 300+ studies. The cycle, REM, jet-lag and wind-down models are built from the primary literature, and every source is listed with its context on the methodology & sources page.
Content is written and maintained by the SleepMaxx Calculator editorial team and checked against those sources. This site is not medically reviewed— no clinician reviews this content, and we would rather say that in plain text than hang a reviewer byline we don't have. These are planning tools built on population averages; for a personal sleep problem, a clinician is the right next step.
You will also not find an Epworth Sleepiness Scale, a STOP-BANG questionnaire or an AHI estimator here. Those are clinical screening instruments: their scores only mean something in the hands of someone who can act on them, and hosting them on a calculator site is a safety problem, not a feature. We exclude them deliberately.
Keep planning
Sleep Cycle Calculator
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The 90-minute rule applied properly — with the falling-asleep time most tools skip.
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