睡眠サイクルと起床時間計算機
ガイド
睡眠サイクルと起床時間計算機
The Sleep Cycle & Wake-Up Time Calculator finds the bedtimes and wake-up times that line up with the natural 90-minute rhythm of your sleep. Waking at the end of a complete cycle — rather than in the middle of deep or REM sleep — leaves you feeling clearer-headed, even when total sleep is shorter than usual. Enter a bedtime to see the wake-up times that complete a whole number of cycles, or enter a target wake-up time to see when you should be in bed. A configurable fall-asleep buffer accounts for the minutes it takes to drift off so the math matches reality, not theory.
使用方法
- モードを選択してください： “I plan to go to bed at…” to plan wake-up alarms, or “I need to wake up at…” to plan a bedtime.
- Enter the time in 24-hour format, or tap Use current time (Sleep now) to start from the current clock.
- Adjust the fall-asleep buffer if you typically take longer or shorter than 15 minutes to drift off.
- The table updates instantly. The ほとんどのページ用に row (5 cycles, 7h 30m) and Ideal row (6 cycles, 9h 0m) are highlighted for easy scanning.
機能
- Bidirectional planning – Convert bedtime → wake-up times, or wake-up time → bedtimes, with a single radio toggle.
- Six cycle options at a glance – Every result from 1 to 6 sleep cycles is shown, so you can pick the option that fits the night.
- Sleep quality labels – Power nap, Short rest, Minimum, Recommended, and Ideal labels make the trade-offs obvious.
- Configurable fall-asleep buffer – Default 15 minutes, adjustable from 0 to 60, so the times match your real sleep onset.
- Sleep-now shortcut – One click fills the time field with the current clock for a quick last-minute plan.
- 100%クライアントサイド – Math runs in your browser; no times are sent to a server.
よくある質問
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Why is a sleep cycle 90 minutes long?
A full sleep cycle moves through light NREM, deep NREM, and REM stages. In healthy adults this loop averages roughly 90 minutes, though individual cycles can range from about 70 to 120 minutes. The 90-minute figure is a reliable starting point because the brain naturally drifts back toward light sleep at the end of each cycle, which is the easiest moment to wake.
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Why does waking up between cycles feel groggy?
Sleep inertia — the disoriented, heavy feeling after an alarm — is strongest when waking from deep NREM (slow-wave) sleep. Deep sleep is dominated by slow brain waves that the body needs several minutes to leave behind. Waking at the end of a cycle, when sleep is lightest, lets you bypass most of that inertia.
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Is it better to get less sleep but on a complete cycle?
Total sleep duration still matters: chronic sleep below about 6 hours is associated with cognitive and health costs. Aligning with cycles is most useful when the choice is between waking 15 minutes earlier or later within an already-short night. Over many nights, prioritise enough total sleep first and cycle alignment second.
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How long does it take the average person to fall asleep?
Sleep latency — the time from lights-out to actually being asleep — averages 10 to 20 minutes for healthy adults. Falling asleep in under 5 minutes can be a sign of sleep deprivation, while taking longer than 30 minutes regularly may indicate insomnia, caffeine sensitivity, or an evening routine that keeps the brain too active.
