Jet Lag Recovery Calculator

About this calculator

Jet lag happens because your internal circadian clock keeps running on the rhythm of your departure time zone while the sun and social schedule around you have shifted, and it takes time, roughly one day per time zone crossed as a common rule of thumb, for the body's clock to resynchronise.

Direction matters because the human circadian rhythm naturally runs slightly longer than 24 hours, which makes it easier to delay the clock (as happens flying west, where the day effectively lengthens) than to advance it (flying east, where the day is compressed and the body has to catch up faster). That's why travellers typically report recovering somewhat faster from westward flights than from eastward ones covering the same number of time zones.

Enter the number of time zones you crossed and whether you flew east or west, and this calculator estimates how many days your body clock will need to catch up.