Jet Lag Recovery Calculator

Jet lag is the clinical mismatch between your internal circadian rhythm and the local time at your destination. Symptoms — daytime fatigue, nighttime insomnia, GI distress, mood disruption, impaired cognition — persist until your master clock (in the suprachiasmatic nucleus) and your peripheral clocks (liver, gut, muscle) re-sync to local time. The body resets at roughly 1 hour per day eastward and 1.5 hours per day westward.

Enter your origin and destination time zones and the date and time of your arrival. The calculator generates a 3- to 7-day schedule of light exposure windows, light avoidance windows, optimal meal times, and (where evidence supports it) timed melatonin doses to shift your circadian rhythm forward or backward as needed.

1. Arrival day: get 30 min of outdoor light immediately after destination noon. Avoid napping past 30 min.
2. Day 2: bright light 7–9 AM local, dim room from 7 PM, melatonin 0.5 mg at 9 PM.
3. Day 3: bright light continues mornings; first true full-night sleep usually here.
4. Day 4: drop melatonin, maintain light schedule.
5. Day 5: full circadian alignment for most travelers.

• Hydrate aggressively in flight — dehydration worsens every jet-lag symptom.
• Avoid alcohol on the plane — it suppresses REM and dehydrates.
• Sleep on the plane only if it aligns with destination night.
• Use eyemask + earplugs for in-flight sleep blocks.
• First meal at destination = breakfast, lunch, or dinner per local time, not body time.

Melatonin works as a circadian shifter, not a sedative. Use 0.3–0.5 mg about 30 minutes before destination bedtime for 3–5 nights post-arrival. Doses of 5–10 mg are popular but not more effective for jet lag — they often cause grogginess and vivid dreams without faster realignment.

Pair the jet lag recovery calculator with the bedtime calculator (to lock in destination-time bedtimes), the sleep cycle calculator (to set arrival-day naps cleanly), and the sleep quality score (to track realignment progress nightly).

Your circadian rhythm has a natural period slightly longer than 24 hours — typically 24.2 hours in adults. This means it is biologically easier to lengthen a day (westward travel) than to shorten one (eastward travel). Crossing six time zones west typically resolves in 4–5 days; crossing six zones east often takes 7–9 days. The eastward asymmetry is also why daylight saving time spring transitions produce measurable spikes in heart attacks, car accidents, and workplace injuries the following Monday.

1. Begin shifting bedtime 30 minutes per day toward destination time, starting 3 days before flying.
2. Adjust meal times in parallel — peripheral clocks in the gut and liver respond strongly to feeding cues.
3. Reduce evening alcohol and caffeine the week of travel.
4. Pre-book a window seat on the side that gives you destination-aligned light during landing.
5. If flying east, consider taking 0.5–1 mg of melatonin 5 hours before destination bedtime, starting 2 days before.

Use the jet lag recovery calculator alongside the bedtime calculator (to set your destination-aligned bedtime), the sleep quality score (to verify recovery), and the caffeine cutoff calculator (to protect the new bedtime). Frequent travelers who run this stack consistently report cutting jet lag duration by roughly 40% versus unstructured recovery.

Standard jet lag rules assume a single direct flight across distinct time zones. Real travel is messier: polar routes that cross more zones than expected, multi-stop trips that re-anchor partial recovery, and frequent route patterns (transatlantic monthly, U.S.-Asia quarterly) that produce cumulative chronic circadian disruption. Each pattern requires different management.

Does melatonin help with jet lag?

Yes, when dosed correctly: 0.5–1 mg taken at destination bedtime for 3–5 nights after eastward travel. Most over-the-counter doses (3–10 mg) are too high and produce morning grogginess that worsens recovery. Less is more.

Is sleeping on the plane helpful?

Strategic sleep on the plane only helps if it aligns with destination night — sleeping during what will be the destination's daytime makes jet lag worse. Use the destination time zone as your guide from the moment you board.

What about jet lag drugs like modafinil?

Modafinil and similar wake-promoting agents can mask jet lag symptoms during the daytime but do nothing to shift the underlying circadian clock. They are appropriate for high-stakes performance windows but not a substitute for proper light, meal, and sleep timing.

How can I prevent jet lag entirely?

Begin pre-shifting bedtime and meal times 3 days before travel, use destination-aligned light exposure on arrival, hold strict destination meal and sleep timing for 5–7 days, and avoid alcohol on the flight and during recovery. Following all four steps reliably cuts jet lag duration by 40–60% in published studies.