Jet Lag Calculator
Enter local departure and arrival details, then compare how your travel pattern may affect adjustment speed, fatigue, and first-day scheduling.
Example Data Table
| Scenario | Shift | Direction | Sleep debt | Estimated recovery | Expected fatigue |
|---|---|---|---|---|---|
| New York to Paris | +6 hours | Eastbound | 1.0 hour | 7.2 days | High |
| Dubai to Bangkok | +3 hours | Eastbound | 0.5 hour | 3.4 days | Moderate |
| Tokyo to Los Angeles | -17 hours | Westbound | 2.0 hours | 15.7 days | Very high |
Formula Used
1. Time-zone shift: destination UTC offset minus origin UTC offset. The absolute value shows the size of your circadian mismatch.
2. Adaptation rate: eastbound trips start near 0.7 zones per day, while westbound trips start near 1.0 zone per day.
3. Rate modifiers: chronotype, age group, light planning, hydration, and melatonin slightly raise or reduce the baseline adaptation rate.
4. Recovery estimate: recovery days = absolute time-zone shift ÷ adjusted adaptation rate.
5. Fatigue score: the score combines time-zone change, arrival timing, sleep debt, in-flight sleep deficit, age, light control, hydration, caffeine pattern, and melatonin support.
6. First sleep window: bedtime and wake time are shifted partway toward the destination clock to create a realistic first-day target.
How to Use This Calculator
Enter local departure and arrival date-times exactly as shown on your itinerary. Add the origin and destination UTC offsets for both airports or cities.
Fill in your normal bedtime, wake time, sleep debt, and how much sleep you expect during travel. Then choose your chronotype and planning options.
Press the calculate button. The results appear above the form, directly below the page header, with recovery time, fatigue level, and action guidance.
Use the export buttons to save the result summary as CSV or PDF for trip planning, coaching notes, or travel wellness checklists.
FAQs
1. What does the recovery estimate mean?
It estimates how many days your body may need to adapt to the new clock. It is a planning aid, not a medical promise.
2. Why are eastbound trips usually harder?
Eastbound travel asks you to fall asleep earlier than usual. Advancing the body clock is often slower than delaying it.
3. Does a longer flight always mean worse jet lag?
Not always. Time-zone change matters more than flight length. However, poor sleep, dehydration, and overnight arrivals can raise fatigue.
4. Why does the calculator ask about chronotype?
Morning and evening types often adapt differently. The calculator uses chronotype to slightly adjust the predicted adaptation rate.
5. Can this help with business travel planning?
Yes. It helps estimate when you may feel sharper, when to schedule naps, and how to place light exposure and caffeine.
6. Should I trust the melatonin advice automatically?
No. The calculator only reflects whether melatonin support may improve adaptation. Personal suitability should be checked with a clinician.
7. What if my destination uses daylight saving time?
Use the actual local UTC offset on your travel date. Seasonal clock changes can alter the true time-zone difference.
8. Does the fatigue score diagnose a sleep problem?
No. The fatigue score estimates travel-related strain only. Ongoing sleepiness, insomnia, or health concerns deserve medical evaluation.