What is the Jet Lag Calculator?
The Jet Lag Calculator provides a rough circadian-adjustment estimate from the number of time zones crossed and direction of travel. It uses average adaptation rates described in the CDC Yellow Book.
How does the Jet Lag Calculator work?
Enter the approximate number of time zones crossed and choose eastward or westward travel. Eastward travel generally requires a phase advance and adapts more slowly on average than westward travel.
What formula or rule does it use?
Estimated adaptation days = time-zone shift ÷ average adaptation rate. CDC Yellow Book cites about 1 hour/day eastward and 1.5 hours/day westward on average. The dynamic “How this answer was calculated” panel substitutes the values you enter into the rule after a valid calculation.
How should you use this calculator?
Use the estimate as general planning context, not a medical prediction. Pair it with the Time Zone Calculator for clock differences, the Flight Time Calculator for route duration, the Travel Days Calculator for trip length, and the Trip Cost Calculator for expenses.
How should you understand the result?
The main result is an estimated number of adaptation days based on the CDC average rate for the selected direction. It also shows the rate used and the size of the time-zone shift.
What are the limitations?
Jet lag varies by individual, sleep history, timing, light exposure, direction, number of zones crossed and other factors. The result is an average educational estimate, not medical advice or a personalized sleep schedule.
Who can use this calculator?
Useful for travelers planning recovery time after long east-west trips across several time zones.
Frequently asked questions about Jet Lag
Sources and methodology
Travel methodology and context are grounded in the following official U.S. sources where applicable. The calculator formula itself is shown transparently above.