Jet Lag Calculator

Estimate jet lag severity and recovery time from a time zone change.

About Jet Lag Calculator

The body clock adjusts more easily westward, because lengthening a day is easier than shortening one. That asymmetry is why eastward travel takes roughly half again as long to recover from. Recovery takes about a day per time zone eastward, which means a trip shorter than the recovery period is spent entirely jet-lagged.

Formula

Jet Lag

Recovery days ≈ time zones crossed ÷ adjustment rate, adjusted for age

adjustment rate: About one hour a day eastward and 1.5 westward
eastward penalty: Advancing the body clock is harder than delaying it

Worked example

With the default values below, Jet Lag Calculator returns Estimated Recovery Time of 8.19. Change any input above and every figure here is recalculated in your browser.

Inputs used

Time zones crossedaccepts 0–14: 8
Direction of travelone of Eastward, losing hours, Westward, gaining hours: Eastward, losing hours
Ageaccepts 1–110 years: 38 years
Flight durationminimum 0 h: 11 h
Sleep obtained on the flightaccepts 0–16 h: 3 h

Results

Estimated Recovery Time: 8.19 days
Jet Lag Severity Score: 14.3
Adjustment Rate: 1.000 hours/day
Sleep Debt Accumulated: 6.17 h
Severity Band: Severe

Step by step

1Values used
2Jet Lag
3Estimated Recovery Time= 8.19 days
4Jet Lag Severity Score= 14.3
5Adjustment Rate= 1.000 hours/day
6Sleep Debt Accumulated= 6.17 h
7Severity Band= Severe

Assumptions and limits

The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is Jet Lag calculated?

Recovery days ≈ time zones crossed ÷ adjustment rate, adjusted for age The body clock adjusts more easily westward, because lengthening a day is easier than shortening one. That asymmetry is why eastward travel takes roughly half again as long to recover from.

Why does Jet Lag matter?

Recovery takes about a day per time zone eastward, which means a trip shorter than the recovery period is spent entirely jet-lagged.

What values do I need to enter?

This calculator takes 5 inputs: Time zones crossed, Direction of travel, Age, Flight duration, Sleep obtained on the flight. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.