Jet Lag Calculator
Estimate how much jet lag to expect on your route and get a suggested sleep and light-exposure plan — including a gradual pre-trip schedule based on your usual bedtime.
Tokyo is 16 hours ahead
Significant jet lag expectedBecause the difference is more than 12 hours, your body clock adjusts the shorter way around: about 8 hours later (as if traveling west).
- Estimated adjustment time
- ~6 days
- Route
- Los Angeles → Tokyo
Sleep: In the 3 days before departure, try going to bed and waking about 1 hour later each day. After arrival, stay up until a normal local bedtime.
Light exposure: Seek bright light in the late afternoon and evening at your destination and avoid bright morning light for the first days. Evening light helps shift your body clock later when traveling west.
Suggested pre-trip sleep schedule
- 3 days before departureBed 12:00 AM · Wake 8:00 AM
- 2 days before departureBed 1:00 AM · Wake 9:00 AM
- 1 day before departureBed 2:00 AM · Wake 10:00 AM
This tool provides general travel planning information and is not medical advice. Consult a healthcare professional about sleep or health concerns.
How Does the Jet Lag Calculator Work?
Jet lag happens when your internal body clock is out of sync with the local day-night cycle at your destination. The bigger the time zone difference, the larger the mismatch. This calculator measures the exact time difference on your travel date, determines whether you are flying east (clock jumps forward) or west (clock falls back), and estimates how long a typical traveler needs to adjust.
It then builds a general plan around the two most useful levers: shifting your sleep gradually before departure, and timing bright light exposure after arrival. These recommendations are informational and based on widely used rules of thumb — everyone adjusts at their own pace.
Frequently Asked Questions
Why is eastward travel usually harder than westward?
Traveling east means going to bed earlier than your body expects, which is harder than staying up later. Most people adjust roughly one time zone per day eastward, but closer to one and a half zones per day westward.
How does light exposure affect jet lag?
Light is the strongest signal for your body clock. Bright light in the morning shifts your rhythm earlier (helpful going east), while light in the evening shifts it later (helpful going west). Timing light exposure well is one of the most effective general strategies for adjusting faster.
Should I adjust my sleep before the trip?
Many travelers find that shifting bedtime by about an hour per day for a few days before departure makes the transition easier. This calculator suggests a gradual pre-trip schedule based on your typical bedtime and direction of travel.
Is this medical advice?
No. This tool provides general travel planning information only and is not medical advice. If you have sleep problems, health conditions, or take medication on a schedule, consult a healthcare professional before your trip.
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