Jet Lag Recovery Calculator
Estimate how many days of jet-lag recovery to expect based on time zones crossed and direction of travel.
What this calculates
The body's circadian clock adjusts about one time zone per day, with eastbound travel taking ~50 % longer than westbound. This calculator gives a rough recovery estimate based on time zones crossed and direction — useful for planning when to schedule important meetings or events after international travel.
Formula & how it works
Recovery days ≈ zones_crossed × (eastbound ? 1.0 : 0.7). Light exposure, melatonin timing, and sleep discipline can speed this. Crossing 8+ zones, factor in 'cumulative' effect — additional sleep debt makes the back-end recovery longer.
Worked example
New York (UTC−5) to Tokyo (UTC+9): 14 time zones, but more commonly counted as 10 going west. Westbound (because faster recovery direction in practice): 10 × 0.7 = 7 days. Returning eastbound: 10 × 1.0 = 10 days. Plan no critical meetings in the first 3 days.
Frequently asked questions
Why is eastbound harder?
The body finds it easier to stay up later (lengthening day, westbound) than to fall asleep earlier (shortening day, eastbound). The circadian clock naturally runs slightly longer than 24 hours, so westbound aligns with that drift.
Do shorter trips fully adjust?
Often not. A 3-day trip across 6 time zones often means you never fully adjust to local time. The body knows you're going back. Pre-shifting before the trip can help.
What helps recovery?
Morning sunlight at destination, strict local meal times, melatonin at local bedtime (0.5-3 mg, well-supported research), avoiding alcohol and screens in the new evening hours. Caffeine timed to local morning, not body time.
Are pilots immune?
No, but they manage. Crew rest rules and scheduled exposure protocols help. Long-haul pilots often work cumulative debt for years before retiring.