Social jetlag calculator: how far does your body "fly" every weekend?
By Kevin Buhl Jakobsen · Everything is worked out in your browser; nothing is saved or sent · Updated 7. Nov 2026
How you sleep
Use the times you actually fall asleep and wake up, not when you get into or out of bed. Take an average of a normal week.
What is social jetlag?
The term comes from chronobiologist Till Roenneberg and colleagues. It describes the gap between when your body would like to sleep, which shows up on free days, and when your social life, mainly work and school, makes you sleep. It is measured by comparing your midpoint of sleep, the moment halfway between falling asleep and waking, on free days and on work days. If you sleep from 23:30 to 06:30 during the week, your midpoint is 3 a.m. If you sleep from 01:30 to 09:30 at the weekend, it is 5:30. The difference of 2½ hours is your social jetlag: like flying 2½ time zones west every Friday and back again on Monday.
It is very common. In Roenneberg's large surveys of Europeans, about two thirds had at least an hour of social jetlag, and around a third had two hours or more. It is largest in night owls and in teenagers and young adults.
Why it matters
Every Monday your body clock has to adjust, and like real jetlag, that takes days. By the time you have adapted, the weekend is back. The result can be tiredness, poorer concentration and low mood. Research has also linked large social jetlag with worse mood and some markers of poorer metabolic health, though researchers are still working out what is cause and what is effect.
The calculator also shows how much longer you sleep on free days. If it's a lot longer, that is a sign you are catching up on sleep you are missing during the week.
How to shrink it
- Keep your wake-up time fairly steady, on free days too: within about an hour of your usual time. If you went to bed late, an early-afternoon nap is better than sleeping until noon.
- Get daylight in the morning. 10–30 minutes outside soon after waking pulls your clock earlier.
- Dim the lights in the evening, and turn your screens down for the last hour or two.
- Move slowly, 15–30 minutes a day, if your rhythm has drifted a long way.
Read more in our articles on social jetlag and on night owls and early birds, and find your best bedtime with the sleep calculator.
General information, not medical advice.
Sources and further reading
- Wittmann M, Dinich J, Merrow M, Roenneberg T (2006). Social jetlag: misalignment of biological and social time. Chronobiology International 23(1–2):497–509.
- Roenneberg T, Allebrandt KV, Merrow M, Vetter C (2012). Social jetlag and obesity. Current Biology 22(10):939–943.