🌐 Social Jet Lag Calculator — How to Use
What This Tool Does
Social jet lag is the gap between your natural sleep midpoint and what your work schedule forces on you. It acts like crossing two time zones every single week.
When to Use It
Calculate it once to understand your baseline. Recheck whenever your schedule changes.
Fields Explained
Workday Bed / Wake
Your typical sleep times on days when you have to be somewhere in the morning.
Free-day Bed / Wake
Your sleep times on days with no morning obligation — weekends or holidays.
Reading the Result
SJL = |Free-day midsleep − Workday midsleep|. Under 1 h is low risk. 1–2 h is moderate. Over 2 h is severe and linked to metabolic and mood problems.
Pro Tips
Even moving your weekend wake time 30 minutes earlier reduces social jet lag meaningfully.
A high SJL usually means you are a natural night-owl forced onto an early schedule.
Bright morning light on weekdays is the fastest way to pull your clock earlier over time.
Try a Sample
Sample scenario
Weekdays: bed 11 PM, up 6 AM. Weekends: bed 1 AM, up 9 AM — a classic work-vs-weekend split.
Expected result: Social Jet Lag 2.5 h · Severe · Workday midsleep 2:30 AM · Free-day midsleep 5:00 AM
🔄 Social Jet-Lag · Sleep Clock Shift · Free Calculator
Social Jet-Lag Calculator
Calculate the difference between your workday sleep clock and your free-day sleep clock — and get practical alignment strategies.