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Chronotype Bedtime Calculator

Pick your chronotype and sleep need to see the bedtime that suits your body clock.

How it is calculated

The tool fixes a sleep midpoint for each chronotype and centres your sleep around it. The midpoints are 02:30 for a morning type, 04:00 for an intermediate type and 05:30 for an evening type. With a sleep need of S hours, half of it is S × 30 minutes. Bedtime is midpoint − S × 30 minutes and wake time is midpoint + S × 30 minutes, wrapping around midnight and rounded to the nearest minute. The sleep need must be between 3 and 14 hours; a value outside that range, or a chronotype other than morning, intermediate or evening, shows no result. If you leave the chronotype blank, intermediate is used. The result is a schedule for a day with no alarm. It is a planning starting point: individual midpoints vary, so a work-day alarm may force you off this timing.

Worked example

An intermediate chronotype needing 7.5 hours of sleep. The midpoint is 04:00, which is 240 minutes after midnight. Half the sleep need: 7.5 × 30 = 225 minutes, or 3 hours 45 minutes. Bedtime: 04:00 − 3:45 = 00:15. Wake time: 04:00 + 3:45 = 07:45. Result: bedtime 00:15, wake time 07:45, midpoint 04:00. Between 00:15 and 07:45 there are exactly 7 hours 30 minutes, the sleep you asked for.

Try this example →

Common mistakes

  • Reading the bedtime as the time you will fall asleep. It is the time to be asleep, so lights out needs to come earlier by however long you usually take to drop off.
  • Entering the time you spend in bed instead of the sleep you need. Time awake in bed does not count, so enter hours of actual sleep.
  • Expecting the schedule to fit a workday alarm. It is built on the sleep midpoint of a free day, so an early alarm can leave you short of the sleep you entered.
  • Typing the sleep need as hours and minutes, such as 7.30 for seven and a half hours. The field is decimal hours, so 7.5 is the correct entry.
  • Picking the chronotype you wish you had. Choose the one that matches when you sleep and wake naturally on free days.

About this calculator

A chronotype describes whether your body's internal clock naturally runs earlier (‘lark,’ or morning type) or later (‘owl,’ or evening type), and chronobiologists commonly summarize it with the sleep midpoint — the point exactly halfway between the time you fall asleep and the time you wake up on a day with no alarm. Building a schedule around that midpoint, rather than an arbitrary bedtime, keeps sleep and wake times aligned with the circadian rhythm your body actually runs on.

This matters because forcing an evening-type person onto an early bedtime, or a morning-type person into a late one, tends to produce social jet lag: the same mismatch between body clock and schedule that causes jet lag from travel, but caused by a daily routine instead. Sleep researchers use midpoint-based scheduling, popularized by tools like the Munich ChronoType Questionnaire, to design more realistic sleep advice than a one-size-fits-all ‘go to bed by 10pm’ rule.

Pick your chronotype and how much sleep you need, and the calculator works back from your natural sleep midpoint to suggest a bedtime and wake time that fit your body clock rather than fighting it.

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