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While I breathe, I hope Newsletter (Turkish)

Sleep / Interactive

Morning person or night owl? Find your mid-sleep time

Your body has an internal clock. For some people it runs early, for others late. The hours you sleep on free days reflect this clock well. Work out your mid-sleep time with six short questions.

Your answers do not leave this page. The calculation runs in your browser; nothing is sent anywhere or saved. It is gone when you close the page.

On free days, do you wake up with an alarm?

How is it calculated?

Mid-sleep is the exact midpoint between the time you fall asleep and the time you wake up. Researchers use mid-sleep on free days to measure the internal clock, because on workdays your timing is usually set by an alarm clock.1,4

Evening types sleep little on workdays and make up for it by sleeping long on free days.1 This extra sleep makes free-day mid-sleep look later than it is. So if you sleep longer on free days than on workdays, the calculation corrects part of this difference.4

The difference between mid-sleep on workdays and on free days is called social jet lag. It describes the mismatch between your body clock and social time; it is largest in evening types.2,4

There is no sharp line between morning and evening types; people are spread over a long range, and dividing them into groups is arbitrary.3,4 To give a rough direction, this page uses two cut-offs: a mid-sleep before 02:30 suggests a morning tendency, and after 04:30 an evening tendency. The cut-offs are about one hour before and after the average weekend mid-sleep (03:26) in a US sample of 53,689 people.5 Mid-sleep also changes with age: it reaches its latest point at the end of adolescence, then moves earlier over the years.5

This page is not a scale or a test; it gives no score and no diagnosis. If you find it hard to fall asleep, feel very sleepy during the day, or your hours keep clashing with your work, you can take your result to a doctor as a note.

For expertsMSF, MSFsc, SJL

The calculation follows the logic of the Munich Chronotype Questionnaire (MCTQ) but does not use its questions. The MCTQ asks about sleep timing on work and free days in detail; here only the time of falling asleep (SO) and waking up are asked, and sleep duration (SD) is the difference between them.1,4

MSF = SOf + SDf/2. If SDf ≤ SDw, MSFsc = MSF; if SDf > SDw, MSFsc = MSF − (SDf − SDweek)/2, where SDweek = (SDw × workdays + SDf × free days)/7. SJL = MSF − MSW; the original definition is the absolute difference, and the signed difference is informative too.4 Jankowski's proposal of an SJLsc corrected for sleep debt simplifies to the difference SOf − SOw.4

People who use an alarm on free days were not included in the MCTQ database distributions.4 The MCTQ was validated against the Horne and Östberg morningness eveningness questionnaire (MEQ), sleep diaries and actigraphy.3 In shift workers, chronotype is calculated from mid-sleep after evening shifts; this page does not take shift patterns into account.4

Sources

  1. Roenneberg T, Wirz-Justice A, Merrow M. Life between clocks: daily temporal patterns of human chronotypes. Journal of Biological Rhythms. 2003;18(1):80-90. doi:10.1177/0748730402239679 · Survey study.
  2. Wittmann M, Dinich J, Merrow M, Roenneberg T. Social jetlag: misalignment of biological and social time. Chronobiology International. 2006;23(1-2):497-509. doi:10.1080/07420520500545979 · Cross-sectional study.
  3. Roenneberg T, Kuehnle T, Juda M et al. Epidemiology of the human circadian clock. Sleep Medicine Reviews. 2007;11(6):429-438. doi:10.1016/j.smrv.2007.07.005 · Review.
  4. Roenneberg T, Pilz LK, Zerbini G, Winnebeck EC. Chronotype and social jetlag: a (self-) critical review. Biology. 2019;8(3):54. doi:10.3390/biology8030054 · Review.
  5. Fischer D, Lombardi DA, Marucci-Wellman H, Roenneberg T. Chronotypes in the US: influence of age and sex. PLOS ONE. 2017;12(6):e0178782. doi:10.1371/journal.pone.0178782 · Cross-sectional study.