Social Jet Lag Calculator

About this calculator

Social jet lag is a term coined by chronobiologist Till Roenneberg to describe the mismatch between your body's natural sleep rhythm and the schedule your work or school life forces on you — measured as the gap, in hours, between the midpoint of your sleep on workdays and the midpoint of your sleep on free days. Someone who sleeps midnight to 6am on weekdays but 2am to 10am on weekends has a sleep midpoint of 3am on workdays and 6am on weekends, a 3-hour social jet lag, comparable to flying three time zones every single week without ever leaving home.

The concept matters because chronic social jet lag of even one or two hours has been linked in sleep research to worse mood, higher body mass index, and increased cardiovascular risk, since it repeatedly forces the body's internal clock to reset. People calculate their own social jet lag to see whether their weekend sleep-in habit is quietly working against them, and shift workers or students with irregular schedules use it to gauge how far their routine has drifted from their body's natural rhythm.

Enter your typical weekday and weekend sleep and wake times, and the calculator computes the size of your social jet lag in hours.