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Sleep Cycle Calculator

Choose when you need to wake up, then see a few realistic bedtimes to work back from. Cycle timing is an estimate, not a promise.

What time do you need to wake up?
Quick:

Adds ~14 min to fall asleep, then counts forward in 90-min cycles

❓ FAQ

How accurate is this estimate? ▾
It is a planning aid, not a medical measurement. Sleep cycles vary from person to person and from night to night, so use these times as a starting point.
How many sleep cycles do I need per night? ▾
Most adults need 5–6 cycles per night (7.5–9 hours). Four cycles (6h) is the minimum for basic function. Six cycles (9h) is optimal for recovery.
Why do I feel tired after 8 hours of sleep? ▾
8 hours = 5 complete cycles + 30 min into a 6th cycle. Your alarm interrupts deep sleep. Try 7.5 hours (5 cycles) instead.
Is 7.5 hours of sleep better than 8 hours? ▾
Often yes. 7.5 hours = 5 complete 90-min cycles. Waking at cycle end means less grogginess. 8 hours wakes you mid-cycle.
How long should a nap be? ▾
20 minutes (power nap) or 90 minutes (full cycle). Avoid 30–60 min naps — they land in deep sleep and cause severe grogginess.

Make tonight easier to plan

Start with the time your morning has to begin. We count backward in approximate 90-minute cycles and include a short wind-down buffer, so you can compare a few workable options.

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Best bedtime by wake-up time

Enter a required wake-up time and get several bedtime options ranked by sleep cycles, from a minimum night to a full recovery night.

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90-minute sleep cycle planning

Waking near the end of a cycle usually feels easier than waking in deep sleep, which is why 7.5 hours can feel better than exactly 8 hours for some people.

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Pair it with caffeine timing

If the recommended bedtime feels impossible, check your last coffee time with the caffeine cutoff calculator and protect the final hours before bed.

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Track weekly sleep debt

Use the sleep debt calculator when one bad night becomes several. Recovery works best when you spread extra sleep across multiple nights.

Sleep decision center

Your bedtime is only one part of the night.

If caffeine, missed sleep, naps, a child’s schedule, jet lag, or morning grogginess is getting in the way, start with the guide that matches what is happening tonight.

10 toolsBedtime, naps, caffeine, sleep debt, jet lag, melatonin, kids, chronotype, workout, hydration.
Problem pagesLong-tail answers for wake-up time, caffeine timing, recovery, and grogginess.
Non-medicalClear educational disclaimers and clinician referral language for persistent problems.
Weekly useBuilt around routines people can repeat, not a one-time novelty calculator.
I need a bedtimeWake-up-first planning and cycle windows. Coffee is ruining sleepHalf-life, cutoffs, and replacement habits. I am behind on sleepThree-night recovery without weekend overcorrection. I wake up foggyTiming, light, alarms, and previous-day checks.
More sleep tools
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Nap Calculator
Power nap timing
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Caffeine Cutoff
Last coffee time
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Workout Timing
Best time to train
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Chronotype Quiz
Lion, Bear or Wolf?
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Sleep Debt
Weekly deficit
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Jet Lag
Recovery plan
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