Social Jet Lag Calculator
Compare work day and weekend sleep to see how far your body clock shifts every week.
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Free social jet lag calculator. Compare work day and free day sleep times to see your sleep midpoint shift, average sleep and how to reduce the gap.
Social jet lag calculator
Enter when you fall asleep and wake up on work days and on free days. The calculator compares the midpoint of your sleep on each to show how far your body clock shifts at the weekend.
What is social jet lag?
Social jet lag is the gap between your sleep timing on work days and free days. If you sleep from 11:30 PM to 6:30 AM on weekdays and from 1 AM to 9:30 AM at weekends, your body clock is shifted by several hours every weekend, a bit like flying across time zones and back again each week.
The size of the gap is measured by comparing the midpoint of sleep on the two kinds of days. Gaps under an hour are small, gaps of one to two hours are moderate and gaps of two hours or more are large. These bands are a rough guide rather than a medical cut off.
How to reduce social jet lag
- Keep your wake time within about an hour of your work day wake time, even after a late night.
- Get bright light soon after waking, because morning light is the strongest cue for the body clock.
- Pay back sleep debt with an earlier bedtime or a short nap, not a very late wake up.
- Move your free day bedtime earlier by 15 to 30 minutes every few days.
- Dim lights and screens in the last hour before bed.
Read more about circadian rhythm, your chronotype and how to fix your sleep schedule.
Frequently asked questions
What is social jet lag?
Social jet lag is the difference between your sleep timing on work days and free days. A large gap can make you feel jet lagged on Monday without any travel.
How do you calculate social jet lag?
Find the midpoint of your sleep on work days and on free days, then subtract one from the other. The size of that gap is your social jet lag.
Is sleeping in at the weekend bad?
A small sleep in of about an hour is usually fine. Very large sleep ins shift your body clock later, which can make Sunday night and Monday morning harder.
Does social jet lag affect teenagers?
Yes, often more, because the teenage body clock tends to run later and school starts early. Keeping a steady wake time and getting morning light can help.
Is jet lag worse flying east or west?
Eastward travel is usually harder because you must fall asleep earlier than your body clock wants. Westward travel asks you to stay up later, which is generally easier.
Is 6 hours of sleep enough?
For most adults it is below the recommended 7 hours. Some people feel fine for a while, but research on chronic sleep restriction found that performance slips even when people do not feel very sleepy. Treat 6 hours as a short night and plan recovery sleep.
How do I move my bedtime earlier?
Shift it by 15 to 30 minutes every two or three days while keeping the wake time fixed, get bright light after waking and dim lights for an hour before bed.
Will waking at the end of a cycle remove morning grogginess?
It can help some people, because waking from light sleep is usually easier than waking from deep sleep. The effect is not guaranteed. Grogginess, known as sleep inertia, usually fades within 15 to 30 minutes and also depends on how much sleep you had and when you wake in your body clock.