Plan bedtimes around sleep cycles — wake refreshed, not groggy.
Plan bedtimes around sleep cycles — wake refreshed, not groggy.
Enter values above and click Calculate — results will appear here with the formula explained.
Sleep moves through roughly 90-minute cycles of light, deep and REM stages. Waking mid-deep-sleep produces the leaden grogginess of sleep inertia even after adequate total rest; waking between cycles feels dramatically lighter.
Working backwards from your alarm, each candidate bedtime subtracts whole cycles plus realistic fall-asleep time — commonly underestimated at 15+ minutes. Three to six cycles span 4½ to 9 hours, letting you trade duration against schedule constraints consciously.
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Sleep moves through roughly 90-minute cycles of light, deep and REM stages. Waking mid-deep-sleep produces the leaden grogginess of sleep inertia even after adequate total rest; waking between cycles feels dramatically lighter. Formula: bedtime = wake − fallAsleep − cycles × 90 min
Sleep Calculator: Plan bedtimes around sleep cycles — wake refreshed, not groggy. Formula: bedtime = wake − fallAsleep − cycles × 90 min. Example: A 07:00 alarm with 15-minute sleep onset: six full cycles means lights out by 21:45; five cycles allows 23:15; four desperate ones, 00:45.
Plan bedtimes around sleep cycles — wake refreshed, not groggy. Formula: bedtime = wake − fallAsleep − cycles × 90 min
| Field | What to enter |
|---|---|
| I want to… | Enter a value |
| Target wake-up time | e.g. 07:00 |
| Minutes to fall asleep | Enter a value |
All fields use the exact formulas shown below — results include step-by-step breakdowns you can verify by hand.
Sleep moves through roughly 90-minute cycles of light, deep and REM stages. Waking mid-deep-sleep produces the leaden grogginess of sleep inertia even after adequate total rest; waking between cycles feels dramatically lighter.
Working backwards from your alarm, each candidate bedtime subtracts whole cycles plus realistic fall-asleep time — commonly underestimated at 15+ minutes. Three to six cycles span 4½ to 9 hours, letting you trade duration against schedule constraints consciously.
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AdSense ready — add NEXT_PUBLIC_GOOGLE_ADSENSE_PUBLISHER_ID
A 07:00 alarm with 15-minute sleep onset: six full cycles means lights out by 21:45; five cycles allows 23:15; four desperate ones, 00:45.
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AdSense ready — add NEXT_PUBLIC_GOOGLE_ADSENSE_PUBLISHER_ID