Adult sleep-window planner
Choose when you want to wake up and how much time you want to set aside. See where that window starts, including when it falls on the previous day.
Plan your window
For adults aged 18 and over. Choose your own duration; the planner does not work out how much sleep you need.
The calculation, without the mystery
Start time = wake-up time minus your chosen duration. A 07:00 wake-up and an 8-hour window gives 23:00 on the previous day. A 16:00 wake-up and an 8-hour window gives 08:00 on the same day.
Times use a simple 24-hour clock. There is no date, time-zone or daylight-saving adjustment: check the elapsed time yourself if clocks change or you travel. The result is a planning aid, not an alarm.
This is not a sleep-cycle calculator, a diagnostic score, sleep-restriction therapy or an ideal-bedtime prescription. It does not assess sleep quality, shift-work suitability, a sleep disorder or safety to drive. A calculated window cannot guarantee rest.
The NHS advises going to bed when sleepy and keeping a regular wake-up time. Speak to a GP if changing habits has not helped, sleep problems have lasted for months, or they make daily life hard to cope with. Do not drive when sleepy.
Guidance checked 28 October 2026. NHS page reviewed 19 March 2024; the AASM/SRS paper is a consensus recommendation, not a trial of this planner. Individual advice may differ.
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