What Is the Jet Lag Recovery Calculator?
Jet lag happens when your internal body clock (circadian rhythm) falls out of sync with the local time at your destination. This calculator gives a quick estimate of how many days your body may need to fully adjust, based on the number of time zones you crossed and the direction you traveled.
How to Use It
Enter the number of time zones between your departure and destination cities, then select your direction of travel. Eastward trips (such as flying from the US to Europe) generally cause worse jet lag because you must advance your body clock, which is harder than delaying it. Westward trips are usually easier to recover from.
The Formula Explained
A widely cited rule of thumb is that the body adjusts roughly one time zone per day when traveling eastward, and slightly faster — about two-thirds of a day per zone — when traveling westward. We model this as $$\text{Recovery Days} = \text{Time Zones} \times \text{rate}$$, where the rate is \(1.0\) for eastward travel and \(0.67\) for westward travel.
Worked Example
Suppose you fly from New York to Paris, crossing 6 time zones eastward. Recovery days = $$6 \times 1.0 = 6 \text{ days}$$ On the return trip westward, recovery = $$6 \times 0.67 \approx 4 \text{ days}$$
FAQ
Is this medical advice? No. This is a general estimate based on common travel rules of thumb. Individual recovery varies with age, sleep habits, and light exposure.
How can I recover faster? Get bright daylight at your destination, stay hydrated, adjust your sleep schedule before departure, and avoid heavy meals and alcohol on the flight.
Why is eastward travel worse? Advancing your body clock (going to bed earlier) is generally harder than delaying it, so eastward jet lag tends to last longer.
