Social jet lag calculator
If you sleep hours later on weekends, your body flies across time zones every Friday and back every Monday. Here's how far.
Work or school days
Free days (no alarm)
Your social jet lag
2 h 8 min
High: like flying 2.1 time zones west every Friday and back every Monday.
Work days
Free days
- Work-day sleep
- 7 h 15 min
- Free-day sleep
- 8 h 30 min
- Chronotype (corrected free-day mid-sleep)
- 4:48 AM
How it's calculated
We find the midpoint of your sleep on work days and on free days, then take the difference. That's the method from the Munich ChronoType Questionnaire (Wittmann, Dinich, Merrow and Roenneberg, 2006). The "corrected" chronotype removes some of the weekend oversleep that comes from paying back weekday sleep debt, so it better reflects your natural clock.
If your free-day sleep is much longer than work-day sleep, you're also carrying sleep debt. Put your week into the sleep debt calculator, and use the schedule fixer to close the gap gradually.
Questions people ask
What is social jet lag?
Social jet lag is the gap between when your body clock wants you to sleep (seen on free days) and when work or school makes you sleep. The term was coined by Till Roenneberg and colleagues in 2006. It is measured as the difference between the midpoint of sleep on free days and on work days.
How much social jet lag is normal?
In Roenneberg’s large European samples, about two-thirds of people had at least one hour of social jet lag and around a third had two hours or more. Under an hour is a reasonable goal.
Is social jet lag bad for you?
Studies have linked larger social jet lag with poorer sleep, more daytime sleepiness and, in some population studies, higher body mass index. These are associations, not proof of cause, but a steadier schedule is a low-risk improvement.
How do I reduce social jet lag?
Narrow the gap from both ends: go to bed a little earlier on work nights, and keep free-day wake times within about an hour of work days. Get morning light on free days too, so your clock doesn’t drift later over the weekend.
Sources
- Wittmann M, Dinich J, Merrow M, Roenneberg T (2006). Social jetlag: misalignment of biological and social time. Chronobiology International, 23(1–2).
- Roenneberg T et al. (2012). Social jetlag and obesity. Current Biology, 22(10).
- Roenneberg T et al. (2019). Chronotype and social jetlag: a (self-) critical review. Biology, 8(3).