😴 Jet Lag Calculator
Enter how many time zones you'll cross and which way you're flying for an estimate of how long adjustment takes — plus tips to ease it.
Estimated time to adjust
≈ 9 days
Rule of thumb: about 1½ days per time zone travelling eastward — which shortens your day and is usually harder.
Easing it:
- Shift your sleep schedule an hour a day toward the destination before you leave.
- Get bright daylight at the right time — morning light helps after eastward flights, evening light after westward.
- Adopt local meal and sleep times on arrival; stay hydrated and go easy on alcohol and late caffeine.
General guidance, not medical advice. The "about a day per time zone" rule and the eastward-is-harder pattern are widely cited (Cleveland Clinic, Sleep Foundation, Better Health Channel); individuals vary, and roughly a quarter of people find the opposite direction harder. 🔒 In your browser.
How the jet lag calculator works
Jet lag comes from your body clock being out of step with local time. A widely-cited rule of thumb is that the body re-syncs at roughly one time zone per day. Because our internal clock naturally runs a little longer than 24 hours, going westward (lengthening the day) is usually easier than going eastward (shortening it), so the tool applies a slower rate — about 1½ days per zone — for eastward trips.
This is general guidance, not medical advice, and people vary widely — roughly a quarter of travellers find the opposite direction harder. Light exposure at the right time, shifting your schedule before departure, and adopting local meal and sleep times on arrival all help you adjust faster than the rule of thumb suggests.
Frequently asked questions
How long does jet lag last?
A common rule of thumb is about one day of adjustment per time zone crossed, so a 6-hour shift takes roughly six days to fully clear — though many people function well sooner and good light and sleep habits speed it up.
Why is flying east worse than flying west?
Eastward travel shortens your day, forcing your body clock to advance, which is harder than delaying it. Since our natural circadian rhythm is slightly longer than 24 hours, westward travel (a longer day) aligns with it more easily.
How can I reduce jet lag?
Shift your sleep toward the destination's time a few days before you travel, get bright daylight at the right time (morning light after eastward flights, evening light after westward), adopt local meal and sleep times on arrival, and stay hydrated while limiting alcohol and late caffeine.
Does the number of time zones matter more than flight length?
Yes. Jet lag is driven by how many time zones you cross, not how many hours you fly. A long north–south flight within one time zone causes travel fatigue but little jet lag; a shorter east–west flight across several zones causes more.
Is this medical advice?
No. It's a general estimate based on widely-cited guidance (Cleveland Clinic, the Sleep Foundation and others). If jet lag seriously affects you or you have a health condition, speak to a healthcare professional.
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How Long Does Jet Lag Last? Why Flying East Is Worse — and How to Cut Recovery in Half
Jet lag lasts roughly one day per time zone flying west, but about 1.5 days per zone flying east. Here's the circadian reason east is harder, and how correctly timed light exposure compresses recovery to 2–3 zones a day.