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✈️ Jet Lag Calculator — Personalised Sleep Recovery Plan

Enter your flight details and get a personalised jet lag recovery plan with target sleep times for your destination.

Jet Lag Facts

1 day/tz
Recovery time eastward per time zone crossed
0.75d/tz
Recovery time westward per time zone crossed
3–4 days
Recovery for a typical long-haul flight (6–8 tz)
10+ days
Full circadian reset for extreme crossings (12 tz)
0.5–3mg
Effective melatonin dose for jet lag

Evidence-Based Jet Lag Recovery Tips

What the research says — not just general travel advice.

☀️
Get morning light at destination immediately
Light is the most powerful circadian synchroniser. Upon arrival, spend 30–60 minutes in outdoor light in the morning (destination time). This resets your clock faster than any supplement.
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Avoid bright light in the evenings (first 2 days)
Especially for eastward travel — evening light at the destination corresponds to daytime at home, which delays your clock in the wrong direction. Use blue-light blocking glasses after 7 PM.
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Take low-dose melatonin at destination bedtime
0.5–3mg of melatonin at destination bedtime for the first 3–5 nights significantly reduces jet lag symptoms and speeds adaptation. Higher doses increase next-day grogginess.
⏰
Stay awake until local bedtime on arrival day
Resisting the urge to sleep at your home daytime hours (which is daytime at your destination) forces faster adaptation. Only take a brief nap (max 20 min) if absolutely necessary.
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Stay hydrated on the flight
Cabin humidity is 10–20% — well below comfortable levels. Dehydration worsens jet lag symptoms significantly. Drink 250ml of water per hour of flight. Avoid alcohol — it suppresses REM sleep and worsens dehydration.
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Exercise at destination time
Physical activity — even a 20-minute walk — helps shift the circadian clock. Time exercise in the morning for eastward travel (helps advance your clock) or afternoon/evening for westward (helps delay it).
Melatonin Guide

How to Use Melatonin for Jet Lag

Jet lag recovery timeline showing adjustment days needed by time zones crossed

Melatonin is the most evidence-backed pharmacological intervention for jet lag. A Cochrane review of 10 randomised trials (Herxheimer & Petrie, 2002) concluded it is remarkably effective at reducing jet lag symptoms, particularly for eastward travel of 5 or more time zones.

The key insight is timing over dose. Taking melatonin at the wrong time can worsen jet lag rather than help it. The circadian clock is a phase-response system — melatonin in the afternoon delays your clock; melatonin in the morning advances it. Only evening use (at destination bedtime) is appropriate for jet lag recovery.

Use the lowest effective dose. Most commercial melatonin tablets are 5–10mg — 5 to 20 times higher than what research shows is effective (0.5mg). Higher doses increase next-day grogginess and suppress endogenous melatonin production over time.

Melatonin Protocol by Travel Direction

✈️ Eastward Travel (harder)
  • Take 0.5–3mg melatonin at destination bedtime (9–11 PM)
  • Continue for 3–4 nights after arrival
  • Combine with morning light exposure at destination
  • Avoid evening bright light (especially screens) at destination
✈️ Westward Travel (easier)
  • Melatonin less critical — natural delay is easier
  • If using: 0.5mg at destination bedtime for 2–3 nights
  • Get bright light in the late afternoon at destination
  • Stay awake as long as possible on arrival day
⚠️ Do Not
Take melatonin in the morning or afternoon at your destination — this pushes your clock in the wrong direction and extends jet lag. Do not use if pregnant. Consult your doctor if taking anticoagulants or immunosuppressants.

Frequently Asked Questions

The human circadian clock runs slightly longer than 24 hours — about 24.2 hours on average. This means it naturally tends to drift later (westward direction). Eastward travel requires the clock to shift earlier — which fights this natural drift. Westward travel is easier because delaying the clock is its natural tendency. This is why most frequent fliers report eastward journeys as significantly more disruptive.

For eastward travel of 4+ time zones: start moving your bedtime 30 minutes earlier per night for 3–5 days before departure. Get bright light exposure in the morning. For westward travel: start going to bed 30 minutes later each night. This partial pre-adaptation reduces jet lag severity on arrival.

Melatonin is a hormonal signal of darkness that tells the circadian system it's time to sleep. Taking melatonin at the destination's bedtime — even when it's daytime at home — helps re-synchronise the internal clock to local time. Research (Herxheimer, 2002) in a Cochrane review of 10 trials found melatonin was effective for jet lag, with the best results for eastward travel of 5+ time zones.

Crossing the International Date Line (180° meridian) can actually reduce jet lag if you travel westward across it, because you're effectively gaining a day. The direction of travel matters more than the dateline crossing itself — what matters is the total time zone difference and whether you're going east or west to get there.

Children adapt relatively quickly — their circadian clocks are more plastic. Older adults adapt more slowly because circadian amplitude (the strength of the sleep-wake signal) weakens with age. The elderly also produce less melatonin naturally, which makes night-time adaptation harder. Give extra buffer time before important commitments after flying with elderly travellers.

For eastward travel: 0.5–3mg at destination bedtime (9–11 PM local) for 3–4 nights. For westward travel: less critical, but 0.5mg at destination bedtime can help anchor your schedule. Key: use the lowest effective dose — 0.5mg is as effective as 5mg in most trials but produces fewer next-day side effects. Never take melatonin at the destination's daytime hours — it pushes your clock in the wrong direction.

Yes — returning east is typically harder than going west, which means for most travellers flying London → New York (westward, easier) followed by New York → London (eastward, harder), the return leg is more disruptive. Build in an extra recovery day before important commitments following an eastward return. The total adaptation time for a round trip is roughly 2–3× the one-way adaptation time.

Yes — melatonin is one of the few jet lag remedies with strong scientific evidence. A Cochrane Review of 10 randomised trials found melatonin taken at the target bedtime reduced jet lag severity significantly for flights crossing 5+ time zones. The recommended dose is low: 0.5–3 mg. Higher doses (5–10 mg, common in US supplements) are no more effective and cause next-day drowsiness. Timing matters more than dose — take it at 10–11 pm destination time regardless of what your body clock says.

It depends on your destination. If you are flying eastward (e.g. London to Tokyo), try to sleep on the plane to arrive partially rested and stay awake until local bedtime. If flying westward (e.g. New York to London), sleeping less on the plane and arriving tired makes it easier to fall asleep at the earlier local bedtime. The goal is to align your first night's sleep with local time as closely as possible.

Airlines use "controlled rest" protocols — short in-seat naps (20–45 minutes) for pilots during long hauls. Crew are also trained in strategic light exposure, melatonin timing, and sleep scheduling. Many experienced crew members maintain a single home time zone mentally and use strategic naps rather than trying to fully adjust to each destination. Frequent adjustment and re-adjustment itself disrupts circadian health, which is why aviation workers have elevated rates of sleep disorders and metabolic conditions.

Jet Lag Recovery — Eastward vs Westward Flights

Eastward travel is consistently harder to recover from than westward travel. Flying east requires advancing your circadian clock (going to sleep earlier than your body wants), which conflicts with the natural human tendency toward a slightly longer-than-24-hour internal day. Flying west requires delaying your clock (staying up later), which is more natural. As a rough guide: westward recovery takes 1 day per time zone crossed; eastward recovery takes 1.5 days per time zone. A 6-hour eastward flight can take 9 days to fully recover from.

How Long Does Jet Lag Last?

Jet lag duration depends on the number of time zones crossed and direction of travel. For short hauls (1–3 time zones), most people adjust within 1–3 days. For long hauls (6–12 time zones), full adjustment typically takes 6–12 days. Athletes and frequent travellers often adapt faster due to practiced sleep routines. Age also matters: older adults typically experience more severe jet lag and take longer to adjust than younger adults.

Jet Lag Tips for Long-Haul Flights

Evidence-based strategies to minimise jet lag: (1) Pre-adjust — shift your sleep 1 hour per day toward your destination time zone for 3 days before departure. (2) Light exposure — get bright light in the morning at your destination for eastward travel; bright light in the evening for westward. (3) Melatonin — 0.5 mg taken at the target destination's bedtime helps re-anchor your circadian clock. (4) Hydration — cabin air is extremely dry; dehydration worsens jet lag symptoms significantly. (5) Avoid alcohol on the flight — it fragments sleep quality even when you feel like it helps you sleep.

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