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Sleep Cycle Calculator

Wake up refreshed, not groggy. Find the perfect bedtime based on your body's natural 90-minute sleep cycles.

What time do you need to wake up?
Quick:

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

❓ FAQ

Is the sleep cycle calculator scientifically accurate? ▾
Yes. The 90-minute sleep cycle is well-established in sleep research. Individual cycles vary between 80–110 minutes, but 90 is a reliable average.
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.
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How this sleep cycle calculator helps

People often search for “what time should I go to sleep if I wake up at 6” or “is 7.5 hours better than 8 hours.” This calculator answers those questions by counting backward from your wake-up time in complete 90-minute sleep cycles, then adding a realistic fall-asleep buffer.

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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.

More sleep tools
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Nap Calculator
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Caffeine Cutoff
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Workout Timing
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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

Sleep cycle quick answers

For short explanations about wake-up windows, naps, caffeine cutoff, and sleep calculator limits, read the Sleep Cycle FAQ.