Jet Lag Calculator

Why direction matters as much as distance

Flying east (forcing your body to fall asleep earlier than usual) is consistently harder to adjust to than flying west (staying awake later, which is closer to most people's natural tendency to drift toward a slightly longer, not shorter, day) — a well-established finding in circadian rhythm research. This calculator applies a commonly cited rule of thumb: roughly one day of adjustment per time zone crossed traveling east, and about two-thirds of a day per zone traveling west.

This is a rough estimate, not a precise prediction

Actual recovery time varies significantly by individual, sleep habits before the flight, exposure to daylight after arrival, and trip length — this gives a reasonable starting expectation, not a guarantee. Deliberately timing daylight exposure and meals to the destination timezone as soon as possible after boarding is the most commonly recommended way to speed up the real-world adjustment beyond this baseline estimate.