How long does jet lag last?

The rough estimate is one day of adjustment per hour of time difference, so a five-hour shift takes about five days for full adjustment. Direction matters — westward travel is easier (about one day per hour) while eastward is harder (about 1.5 days per hour) — and good pre-trip preparation can cut adjustment time roughly in half.

Why is eastward travel worse?

The body's natural rhythm is slightly longer than 24 hours, so westward travel effectively extends the day, which is compatible with that drift. Eastward travel shortens the day, which runs counter to the natural rhythm. Crossing six or more hours eastward is particularly difficult.

How can I reduce jet lag?

A handful of strategies actually work. Adjust your sleep gradually one or two days before the trip, stay hydrated and avoid alcohol or caffeine during the flight, time light exposure strategically (morning sun shifts forward, evening sun shifts back), use a small dose of melatonin if your doctor approves, time meals to the local schedule, and move during the flight.

Should I sleep on the plane?

It depends on the direction and arrival time. If you arrive in the morning at the destination, try to sleep during the flight so you land rested. If you arrive in the evening, stay awake during the flight so you are tired at local bedtime. The goal is to align your in-flight sleep with the destination's schedule.

Yes, for many people. A small dose of 0.5 to 3 mg taken at the right time helps shift the circadian rhythm — usually at bedtime in the destination time zone. Effects vary by individual, and some interactions with medications exist, so consult your doctor first.

What about jet lag for short trips?

For trips under three days, the usual advice is not to try to fully adjust. Stay on home time and schedule activities during your normal hours. Adjusting and then readjusting is more disruptive than not adjusting at all when the trip is short.

Is the data sent anywhere?

No. Jet lag calculation is pure JavaScript using time zone math, running entirely in your browser. Your travel details stay local.

Jet Lag Calculator

Estimate jet lag recovery time and get personalized tips based on time zone difference, direction of travel, and departure time.

Calculators Date & Time

Instant results

Departure City

Arrival City

About Jet Lag

Jet lag occurs when your internal body clock (circadian rhythm) is out of sync with the local time at your destination. Symptoms include fatigue, insomnia, difficulty concentrating, digestive issues, and mood changes. The general rule is that it takes about 1 day to recover for every 1.5 hours of time zone change. Light exposure is the most powerful tool for resetting your circadian rhythm.

How to Use Jet Lag Calculator

Enter origin and destination

Pick the departure and arrival cities. The tool calculates the time zone difference automatically.

Set flight times

Enter your departure and arrival dates and times. The tool factors in flight duration and the time of day you arrive.

View jet lag estimate

Severity (mild, moderate, or severe), expected adjustment time, and the key factors at play (direction and time difference) all show up here.

Get strategy recommendations

The tool produces personalized strategies — pre-trip preparation, light exposure timing, sleep adjustments, and melatonin guidance — tailored to your specific trip.

When to Use Jet Lag Calculator

Travel planning

Long-distance travel disrupts your sleep, and the calculator helps estimate how severe the jet lag will be, plan an adjustment strategy, and even optimize your arrival time. It earns its keep with business travelers, vacation planners, and frequent flyers who do this regularly.

Pre-trip adjustment

Gradually shifting your sleep schedule before you leave can reduce jet lag dramatically. The calculator suggests when to start adjusting and how much to shift each day, which matters most for critical trips like presentations and athletic competitions.

Recovery planning

After you return home, the calculator estimates how long full recovery will take and lays out an optimal sleep schedule to get there. It is especially useful when business meetings are scheduled shortly after a long trip.

Sports and medical applications

Athletes traveling for competition and patients traveling for treatment both benefit from adjustment plans built around peak performance or therapy windows. Trainers, medical teams, and the athletes themselves rely on this kind of timing.

Jet Lag Calculator Examples

5-hour time difference

Input

NYC to London (5 hours forward). Trip duration: 1 week.

Output

Adjustment: ~3-5 days. Strategies: start shifting bedtime 1-2 days before. Light therapy upon arrival. Avoid alcohol. Stay awake until local bedtime first day.

Standard jet lag advice for a moderate time difference. Most people adjust at roughly one day per hour of difference, so five hours would be five days, but proactive strategies cut that down to three to five days.

Significant time change

Input

California to Tokyo (16 hours forward, perceived as 8 hours back). Trip: 2 weeks.

Output

Major jet lag expected. Pre-adjustment recommended: 7-10 days before, gradually shift sleep. Light exposure scheduling crucial. May need: melatonin (consult doctor), strict sleep hygiene.

Crossing the date line creates a large time shift. The body adjusts naturally at about an hour per day, and preparation speeds that up. Direction matters too — westward travel is usually easier than eastward.

Short trip, large difference

Input

Paris to Tokyo for 3-day business trip

Output

Don't fully adjust. Stay on home time as much as possible. Schedule meetings during your normal alert hours (might be early morning or late evening locally).

For short trips across large time differences, adjusting twice (there and back) is more disruptive than not adjusting at all. This is the standard strategy for international business trips of three days or less.

Tips & Best Practices for Jet Lag Calculator

1.Direction matters. Westward travel (gaining time) is easier than eastward (losing time) because the body's natural rhythm tends to extend rather than shorten.
2.Sunlight is the most powerful tool you have. Morning sun helps shift forward, evening sun helps shift back, and strategic light exposure based on direction is crucial.
3.Stay hydrated. Dehydration mimics jet lag fatigue, so drink water during the flight and keep alcohol and caffeine to a minimum.
4.Move during the flight. Light exercise on long flights helps circulation, reduces stiffness, and eases jet lag once you land.
5.Melatonin can help. A small dose of 0.5 to 3 mg at the right time helps shift the circadian rhythm, but talk to your doctor first.
6.Pre-adjust gradually. Shifting your sleep by one or two hours per day before leaving cuts post-arrival adjustment significantly, which is worth the inconvenience for critical trips.

Frequently Asked Questions

Jet lag happens when your body's circadian rhythm (its roughly 24-hour cycle) is mismatched to local time. Travel disrupts sleep timing, hormone production (melatonin and cortisol), digestion, and body temperature regulation, and the symptoms include fatigue, insomnia, concentration problems, mood changes, and gastrointestinal upset.

Jet Lag Calculator

About Jet Lag

How to Use Jet Lag Calculator

Enter origin and destination

Set flight times

View jet lag estimate

Get strategy recommendations

When to Use Jet Lag Calculator

Travel planning

Pre-trip adjustment

Recovery planning

Sports and medical applications

Jet Lag Calculator Examples

5-hour time difference

Significant time change

Short trip, large difference

Tips & Best Practices for Jet Lag Calculator

Frequently Asked Questions

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