Night toolkit / 02
Sleep window planner
Waking mid-cycle is why nine hours can somehow feel worse than seven and a half. This planner works backwards from your alarm in whole ~90 minute cycles, adds about 15 minutes to fall asleep, and checks each option against the recommended range for your age.
Recommended for adult (26-64): 7 to 9 hours per night (National Sleep Foundation consensus, 2015).
Tonight's candidate windows
6 cycles
In range21:30
Lights out
In bed by 21:15
9 h of sleep before 06:30
5 cycles
In range23:00
Lights out
In bed by 22:45
7.5 h of sleep before 06:30
4 cycles
Short night00:30
Lights out
In bed by 00:15
6 h of sleep before 06:30
Below the recommended range: an occasional fallback, not a plan.
Why whole cycles?
- A night is a chain of cycles, each moving through light, deep and REM sleep.
- Waking from light sleep at the end of a cycle usually feels easier than being pulled out of deep sleep mid-cycle.
- Cycles are not exactly 90 minutes: they range from roughly 80 to 110 minutes and lengthen through the night, so treat windows as guidance and keep your wake time constant.
- Consistency beats arithmetic: the same window every night trains your body clock better than a perfect one-off calculation.
Sources
- National Sleep Foundation's sleep time duration recommendations Sleep Health (Hirshkowitz M et al), 2015Age-band sleep duration ranges used by this planner.
- Recommended amount of sleep for a healthy adult: a joint consensus statement J Clin Sleep Med (Watson NF et al, AASM and Sleep Research Society), 2015Adults should sleep 7 or more hours per night on a regular basis.
- Your Guide to Healthy Sleep National Heart, Lung, and Blood Institute (NIH)Sleep cycles average roughly 90 minutes and vary between people and across the night.
Last reviewed: 2026-07-16
Pair it
A bedtime window only works if caffeine is not still arguing with it. Chart your day on the caffeine curve, then find your natural timing with the chronotype check.