How long does jet lag last?

Direct answer

Without any intervention, jet lag lasts roughly one day per time zone crossed eastward and one day for every 1.5 time zones crossed westward. A 6-zone eastward trip (e.g. London → Singapore) takes around 6 days to fully clear. A 6-zone westward trip takes around 4. With well-timed light exposure, controlled sleep timing, and low-dose melatonin, you can compress those numbers by 30–50%.

The single biggest variable is direction of travel, not flight length, age, or fitness.

Why it matters for long-haul economy

The duration of jet lag determines how much of your trip is degraded. If you fly to Tokyo for a 5-day business trip from London (8 time zones east) and do nothing about it, you are functionally jet-lagged for the entire trip and partway through your return. Knowing the actual timeline lets you plan: when meetings matter, when to commit to a workout, when to drive, when to make decisions.

The estimates below come from the CDC Yellow Book, peer-reviewed circadian research, and post-2000 sleep medicine consensus.

The baseline numbers (no intervention)

Time zones crossed	Eastward	Westward
3	~3 days	~2 days
5	~5 days	~3.5 days
7	~7 days	~5 days
9	~9 days	~6 days
11	~11 days	~7.5 days

These are averages. Individual recovery varies by ±30%.

The asymmetry has one cause: humans have an internal cycle of roughly 24.2 hours (Aschoff, 1965). Delaying the clock (westward) aligns with that bias. Advancing it (eastward) does not.

We go deeper on this in Eastward vs westward jet lag: what actually differs.

What “jet lag is over” actually means

There are three different finish lines, and most articles don’t distinguish them.

1. Subjective adaptation (the easy one)

You stop feeling obviously jet-lagged. Usually 60–70% of the way through full recovery. For a 6-zone east trip, this is around day 4.

2. Sleep consolidation

You sleep through the night and wake at the local target time without effort. This usually arrives around day 5–7 for a 6-zone east shift.

3. Full circadian alignment

Core body temperature minimum, cortisol peak, and melatonin onset have all migrated to align with local time. This is the latest finish line — often a day or two after sleep feels normal.

For most travel, finish line #2 is what matters. Performance, judgement, and mood track sleep consolidation more closely than the deeper hormonal markers.

What shortens jet lag

Four interventions consistently move the timeline in published trials.

Timed light exposure (the biggest lever)

Light is the primary regulator of circadian phase. Get it wrong and you delay recovery; get it right and you can compress eastward adaptation by 1–2 days on a 6-zone shift.

Eastward: seek bright morning light at the destination, avoid late-afternoon and evening light for the first 3–4 days.
Westward: seek evening light at the destination, avoid bright light for the first hours after waking.

The jet lag calculator outputs the exact light-seek and light-avoid windows for your route.

Low-dose melatonin (eastward only)

0.5 mg taken in the local evening before bed, eastward direction, accelerates phase advance. The dose matters: 0.5 mg outperforms higher doses for circadian shifting (Burgess et al., 2010). Higher doses cause sedation without faster shift.

Melatonin is not useful for westward travel — you don’t need to advance your clock.

This is general circadian-shifting guidance, not medical advice. Talk to a doctor before adding any supplement.

Pre-trip sleep shifting

Starting 2–3 nights before departure, shift bedtime by 30–60 minutes per night in the direction of travel. Eastward: earlier. Westward: later.

This buys you 1–2 zones of pre-adaptation. On a 6-zone shift, that’s the difference between starting recovery from -6 vs starting from -4.

Avoiding the wrong nap

A 90-minute afternoon nap on arrival day, eastward, will sabotage your first night and add a full day to recovery. If you must nap, cap it at 20 minutes before 3pm local.

What does not change jet lag duration

Several common pieces of advice have no evidence behind them.

Hydration: important for in-flight comfort and reducing post-flight grogginess, but doesn’t accelerate circadian shift.
Avoiding alcohol on the flight: improves sleep quality during and after, doesn’t shift the clock.
Cabin pressure / aircraft type: the 787 and A350 cabins are pressurised lower than older aircraft, which reduces fatigue but not jet lag itself.
Compression socks: prevent DVT and reduce ankle swelling. No circadian effect.
Adaptogen supplements, blue-light blockers worn 24/7, “jet lag diets”: no replicated evidence.

These either help with comfort or do nothing. None of them speed up the body clock.

Worked example — London → Tokyo (9 time zones east)

Without intervention: ~9 days to fully recover.

With protocol:

3 nights pre-flight: shift bedtime 45 min earlier each night → effective starting point shifts from 9 zones to ~7
In-flight: align sleep window to destination night where possible
Day 1 in Tokyo: bright light 7am–10am local, avoid bright light after 3pm, 0.5 mg melatonin at 9:30pm, in bed by 10pm
Days 2–4: repeat light protocol, taper melatonin

Realistic recovery: 5–6 days vs 9. A 35–45% compression.

Worked example — New York → Los Angeles (3 time zones west)

Without intervention: ~2 days.

With protocol:

Pre-flight: stay up 45 min later each night for 2 nights
Arrival evening: outdoor light until ~9pm local
No melatonin needed

Realistic recovery: ~1 day.

When jet lag is not actually jet lag

If symptoms persist past the timelines above, the cause is usually one of:

Travel fatigue — distinct from circadian misalignment, caused by the trip itself (cramped sleep, dehydration, schedule disruption). Resolves in 1–2 days regardless of time zones.
Sleep debt — you arrived already short on sleep. Doesn’t resolve until you actually recover the debt.
Underlying sleep disorder — long-haul travel can unmask insomnia or delayed sleep phase. Worth investigating if recovery routinely takes much longer than the numbers above.

Use the tool

The calculator turns route + departure time into a day-by-day schedule with exact light, sleep, and melatonin windows for your direction.

Open the jet lag calculator

FAQ

How long does jet lag last after a long flight? Roughly 1 day per time zone east, or 1 day per 1.5 zones west, without intervention. A 6-zone east trip is about 6 days. With a timed light + sleep protocol, expect 3.5–4 days.

Does jet lag get worse with age? Mildly. Older adults often show slower phase shifts, but the difference is smaller than the difference between eastward and westward.

Is jet lag worse going east or west? East is consistently harder because it requires a phase advance, which conflicts with the body’s >24-hour natural cycle.

How long is jet lag for an 8-hour time difference? Eastward: 7–8 days without intervention, 4–5 days with protocol. Westward: 5–6 days without intervention, 3–4 days with protocol.

Can you avoid jet lag entirely? Not for shifts above 3 zones. You can compress it significantly with light timing and melatonin, but the underlying circadian shift takes biological time.

Why does jet lag feel worse on day 2 than day 1? Adrenaline and the novelty of arrival mask symptoms on day 1. Day 2 is usually when the actual sleep debt and circadian misalignment hit hardest.

Does flying first class reduce jet lag? It improves sleep quality on the flight, which helps with travel fatigue. It does not change the circadian shift required at destination.

Should you nap on arrival day? Only a short nap (under 20 min, before 3pm local). Longer naps push the first night’s sleep later, delaying adaptation.

Sources

CDC Yellow Book, 2026 edition: Jet Lag Disorder
Eastman & Burgess, 2009, Sleep Medicine Clinics: How To Travel the World Without Jet Lag
Burgess et al., 2010, Journal of Clinical Endocrinology & Metabolism: low-dose melatonin and phase advance
Waterhouse et al., 2007, The Lancet: Jet lag: trends and coping strategies
Aschoff, 1965: human free-running circadian period