A jet lag recovery calculator estimates how long it takes your body to adjust after crossing time zones, and gives you a day-by-day light exposure schedule to speed up the process. Light is the most powerful tool for resetting your circadian rhythm — this calculator tells you exactly when to seek it and when to avoid it.
Your Flight Details
- • Eastward = 1 day recovery per time zone (harder)
- • Westward = 0.75 days per time zone (easier)
- • Light exposure is the #1 circadian clock resetter
- • Based on published chronobiology research
How to Use the Jet Lag Recovery Calculator
Jet lag is not just tiredness — it is your body's internal clock being out of sync with the local day-night cycle. Your circadian rhythm controls sleep, hunger, hormone release, and digestion, all tuned to your home timezone. Recovery means systematically shifting that clock to match your destination.
Step 1: Enter Your Time Zones
Select your departure and arrival time zones. The calculator determines the difference in hours and direction (eastward vs. westward). Flying from New York (UTC-5) to London (UTC+0) is 5 hours east. Flying from Sydney to Los Angeles is about 17 hours west — which wraps around and is actually shorter going east, but this tool calculates the actual directional shift.
Step 2: Enter Your Arrival Time
Your arrival time determines when to start seeking light on Day 1. Arriving at 2am means your light exposure starts the next morning. Arriving at 3pm means you should seek outdoor light immediately and push through to local bedtime.
Following the Light Schedule
Each day's light schedule tells you when to get bright outdoor light (which advances or delays your clock depending on direction) and when to avoid it. Even 20-30 minutes of morning sunlight has a measurable effect on circadian phase. Bright light therapy lamps (10,000 lux) can substitute for sunlight when outdoor exposure is impractical.
Melatonin as a Clock Adjuster
Melatonin is a sleep signal, not a sedative. Low doses (0.5mg — often labeled as "physiological dose") taken at your destination's bedtime signal your brain that it's nighttime in the new timezone. Research shows 0.5mg is as effective as 5mg for clock shifting, with far fewer side effects. Do not take melatonin during the destination's daytime — it will confuse your clock further.
For Long-Haul Travelers
For crossings of 8+ time zones (e.g., New York to Singapore is 13 hours), consider pre-adapting 2-3 days before departure by shifting sleep and meal times toward the destination schedule. This reduces the shock on arrival and can cut recovery time by 1-2 days. Apps like Timeshifter are designed specifically for this purpose for elite athletes and astronauts.
FAQ
Is this jet lag recovery calculator free?
Yes, completely free. No account required. All calculations run locally in your browser.
Is my data safe when using this tool?
Yes, everything runs in your browser. No data is sent anywhere.
How long does jet lag take to recover from?
The general rule is approximately 1 day per time zone crossed when flying east, and about 0.75 days per time zone when flying west. A 6-hour eastward flight causes roughly 5-6 days of jet lag symptoms. Individual recovery varies — fitness, sleep quality, and how strictly you follow a light exposure schedule all affect recovery speed.
Why is eastward travel worse than westward?
Flying east means you are advancing your body clock — you arrive when your body thinks it should still be night. Flying west delays your body clock, which is more natural since your body's internal clock naturally runs slightly longer than 24 hours. Most people find westward jet lag easier to manage.
Does light exposure actually help jet lag?
Yes, light is the most powerful signal that resets your circadian rhythm. Bright morning light tells your body 'it's daytime now,' suppressing melatonin and advancing your clock. Avoiding bright light at the wrong times prevents unwanted clock shifts. Timing light exposure to your destination's schedule is the scientifically validated approach used by athletes, astronauts, and shift workers.
When should I take melatonin for jet lag?
For eastward travel, take 0.5-3mg melatonin at your destination's bedtime for the first 3-4 nights. For westward travel, melatonin is less critical. Low doses (0.5mg) are as effective as high doses (5mg) with fewer side effects. Timing is more important than dose. Avoid taking melatonin during your destination's daytime — it can make adaptation worse.
Should I sleep on the plane?
It depends on your arrival time. If arriving in the morning at your destination, try to stay awake on the flight so you can sleep at local bedtime. If arriving in the evening, sleep on the plane if possible to reduce fatigue on arrival day. Ear plugs, eye masks, and neck pillows make a real difference. Avoid alcohol — it fragments sleep quality significantly.