Jet Lag Calculator
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What Your Result Means
- Time Zones Crossed: The absolute difference between your origin and destination time zones, adjusted for the shortest path around the 24-hour clock.
- Direction of Travel: Eastward travel (losing hours) is harder than westward travel (gaining hours) because it's easier for your body to extend a day than shorten it.
- Estimated Recovery: The number of days your body typically needs to fully adjust to the new time zone, accounting for age and direction.
- Severity: A rating of how challenging the jet lag will be. Mild is 1-3 zones, Moderate is 4-6, and Severe is 7 or more.
How This Calculator Works
This calculator estimates jet lag recovery time using the relationship between time zones crossed, travel direction, and age. Eastward travel requires about 1 day per zone crossed; westward travel requires about 0.67 days per zone. Age multipliers adjust for biological differences: people under 30 recover faster (0.85x), ages 30-50 use the standard rate (1.0x), and those over 50 typically take longer (1.3x). These are population averages; individual recovery varies significantly based on sleep habits, light exposure, and personal resilience.
Quick Questions
Why is eastward travel harder than westward?
Your circadian rhythm (internal body clock) runs slightly longer than 24 hours. It's easier to extend your day by staying awake (westward) than to compress it (eastward), so westward adjustment is typically faster.
When should I take melatonin?
Take melatonin 2-3 hours before your desired local bedtime at your destination to help shift your internal clock forward (eastward travel). For westward travel, avoid evening light and melatonin. Always consult a healthcare provider before starting any supplement.
Can I speed up recovery?
Yes—light exposure is the strongest reset signal. Seek morning light for eastward travel and evening light for westward travel. Adjust your sleep schedule days before travel, stay hydrated, exercise, and eat meals at local times to anchor your circadian rhythm.
Sources
- National Center for Biotechnology Information (NCBI) — Circadian rhythm physiology and jet lag mechanisms
- The Sleep Doctor — Evidence-based sleep and travel guidance
- Sleep Foundation — Circadian rhythm adjustment strategies
Method & review
Estimate only. Results reflect your inputs and standard formulas. Double-check important decisions independently.