Social jet lag calculator
Social jet lag is the mismatch between your body clock on work days and free days — usually measured as a difference in mid-sleep. We infer bedtimes from each wake time and the same sleep duration on both schedule types (change it if weekends differ).
Work-day mid-sleep (approx.)
02:30
bed 22:30 → wake 06:30
Free-day mid-sleep (approx.)
05:00
bed 01:00 → wake 09:00
Social jet lag (free minus work mid-sleep): +2.5 h (2.5 h magnitude)
A wide split between work and free-day sleep timing. Chronotype research (Munich ChronoType / social jet lag literature) links larger social jet lag to higher mortality hazard in some cohorts — treat this as a prompt to stabilize wake time across the week, not panic.
Roenneberg, Wittmann, and colleagues popularized social jet lag in population chronotype work; effect sizes mix behavior, light, and genetics — this calculator is a didactic estimate, not a diagnosis.
Educational estimates only. Sleep and caffeine metabolism vary widely. This is not medical advice; talk to a clinician if you have insomnia, apnea, or other conditions.