Jet Lag Calculator

Enter your route and sleep schedule to get your recovery timeline, melatonin timing, and a day-by-day plan based on circadian science.

Circadian Science Melatonin Timing Light Exposure Plan

At home (origin)

At home (origin)

Based on circadian research. Melatonin suggestions are educational, not medical advice.

How Long Does Jet Lag Last? Complete Reference Table

Recovery time depends on both the number of time zones crossed and the direction of travel. Flying east is consistently harder than flying west:

Time Zones Crossed Direction Recovery Time Severity
1 to 3 zonesEither1 to 2 daysMild
4 to 6 zonesWest3 to 4 daysModerate
4 to 6 zonesEast4 to 6 daysModerate to Severe
7 to 9 zonesWest5 to 7 daysSevere
7 to 9 zonesEast6 to 9 daysSevere
10 or more zonesEither7 to 10 daysVery Severe

Why is flying east harder than west?

Your circadian clock naturally runs at about 24.2 hours, slightly longer than a calendar day. Flying west extends your day (easier for your biology), while flying east compresses it (harder). This is why eastward recovery takes 25 to 50 percent longer.

Jet Lag Symptoms

Jet lag is a temporary circadian rhythm disorder caused by rapid travel across multiple time zones. The most common symptoms include:

😴 Daytime fatigue

Feeling exhausted during local daytime hours

🌙 Nighttime insomnia

Difficulty falling or staying asleep at destination

🧠 Brain fog

Poor concentration, memory lapses, mental cloudiness

😤 Mood swings

Irritability, anxiety, or low mood without reason

🤢 Digestive issues

Constipation, diarrhea, nausea, or appetite loss

⚡ General malaise

Flu-like feeling without actually being sick

When symptoms are more severe

  • More than 5 time zones crossed
  • Flying eastward
  • Poor sleep quality on the flight
  • Alcohol consumed during flight
  • Age 45 and above (slower circadian adaptation)

How to Use Melatonin for Jet Lag

Melatonin is not a sleeping pill. It works by shifting your circadian clock, not by forcing sleep. Used correctly, it can cut your recovery time nearly in half.

Flying East (e.g. New York to London)

  • Take 0.5mg at new destination bedtime (10 to 11 PM local)
  • Start 1 to 2 nights before departure
  • Continue for 3 to 4 nights at destination
  • Combine with morning light exposure (7 to 9 AM local)

Flying West (e.g. London to New York)

  • Usually not needed for westward travel
  • Only if unable to sleep past midnight at destination
  • Take 0.5mg at destination midnight if needed
  • Evening light exposure helps more than melatonin
Dosage note: Research shows 0.5mg is as effective as 5mg for jet lag with significantly fewer side effects. Higher doses may cause next-day grogginess. Always consult your doctor before use.

How to Prevent Jet Lag: 3-Day Pre-Flight Plan

Shifting your sleep schedule gradually before departure is one of the most effective jet lag prevention strategies. Start 3 days before your flight:

Flying East (toward sunrise)

Day minus 3

Sleep 30 minutes earlier than usual

Day minus 2

Sleep 1 hour earlier than usual

Day minus 1

Sleep 1.5 hours earlier than usual

Flying West (toward sunset)

Day minus 3

Sleep 30 minutes later than usual

Day minus 2

Sleep 1 hour later than usual

Day minus 1

Sleep 1.5 hours later than usual

On the plane

  • Set your watch to destination time immediately when you board
  • If it is night at destination: sleep on the plane
  • If it is day at destination: stay awake and walk the aisle
  • Avoid alcohol entirely (doubles recovery time)
  • Drink 250ml of water per hour of flight
  • Use an eye mask and earplugs to control light exposure

Frequently Asked Questions

How long does jet lag last?

Jet lag typically lasts about 1 day per time zone crossed, though flying east adds 25 to 50 percent extra recovery time. A 6-hour eastward flight (like New York to London) may take 5 to 7 days for full adjustment without intervention, but can be reduced to 3 to 4 days with proper light exposure and melatonin timing.

Is jet lag worse flying east or west?

Flying east is consistently harder. Your circadian clock naturally runs at 24.2 hours, so extending the day (westward) is easier than compressing it (eastward). Most people find eastward travel about 25 to 50 percent harder to recover from.

Does melatonin help with jet lag?

Yes, when used correctly. Melatonin at 0.5mg taken 30 to 60 minutes before local bedtime at your destination helps shift your circadian clock. It works best for eastward travel. Research shows lower doses (0.5mg) work as well as higher doses with fewer side effects. Consult your doctor before use.

How many time zones cause jet lag?

Crossing 2 or more time zones can trigger noticeable jet lag. Below 2 zones, most people adapt naturally within a day. At 3 or more zones, deliberate interventions like light exposure timing and melatonin become significantly beneficial.

What is the fastest way to recover from jet lag?

The combination that works best: adapt to local meal and sleep times immediately upon arrival, seek morning light when flying east or evening light when flying west, use 0.5mg melatonin before local bedtime, drink plenty of water, avoid alcohol, and take only short naps (under 20 minutes) before 3 PM if needed.

Can light therapy help with jet lag?

Yes. Light is the strongest signal your brain uses to set its internal clock. Morning light at your destination shifts your clock earlier (ideal for eastward travel). Evening light shifts it later (ideal for westward travel). A 10,000 lux light therapy lamp for 20 to 30 minutes can be very effective. Sunlight works best.

How can I avoid jet lag before flying?

Start shifting your sleep schedule 3 days before departure: move bedtime 30 to 60 minutes earlier each day for eastward travel, or later for westward travel. Avoid alcohol in the days before travel, stay hydrated, and get good sleep the nights before your flight. Even partial pre-adjustment significantly reduces jet lag severity.