Your general adjustment plan
- Enter your trip details above to see suggested tips.
These are general informational tips, not medical advice.
Jet Lag Calculator
Updated July 2026
Enter how many time zones you are crossing and which direction you are flying to estimate how many days it may take your body clock to adjust — plus a short, general plan of light-exposure and sleep-timing tips. Everything runs privately in your browser.
Jet lag roughly follows one day of adjustment per time zone crossed, and traveling east is usually harder than west. Crossing 6 time zones eastward may take about 5–6 days to fully adjust.
How many hours your destination clock differs (1–12).
Estimated time to adjust
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Time zones crossed
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Direction
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How this jet lag calculator works
Jet lag happens when your internal body clock — your circadian rhythm — is still set to the time zone you left while the clock on the wall has moved on. Until the two line up, you can feel sleepy at the wrong times, struggle to fall asleep, and notice dips in energy, appetite and concentration.
A widely used rule of thumb is that the body re-synchronizes at roughly one time zone per day. Direction matters too: flying east shortens your day and asks your clock to advance, which most people find harder, while flying west lengthens your day and is usually easier to absorb. This calculator estimates adjustment days as zones × 1.0 for eastward travel and zones × 0.8 for westward travel, rounded to the nearest day.
Worked example: crossing 6 time zones eastward gives 6 × 1.0 = 6, so about 6 days to adjust. The same 6 zones westward gives 6 × 0.8 = 4.8, rounded to about 5 days. That matches the general guidance that a six-zone eastward trip can take roughly 5–6 days.
| Time zones crossed | Eastward (≈ days) | Westward (≈ days) |
|---|---|---|
| 2 | 2 | 2 |
| 4 | 4 | 3 |
| 6 | 6 | 5 |
| 8 | 8 | 6 |
| 10 | 10 | 8 |
| 12 | 12 | 10 |
Reference note: these figures are general estimates only. Actual recovery varies with age, sleep habits, flight timing, light exposure and individual differences. This is not medical advice.
Frequently asked questions
- How long does jet lag last?
- As a rough rule, the body adjusts at about one time zone per day, so six zones might take roughly five to six days. The exact time varies by person, direction, sleep habits and light exposure — these are general estimates only.
- Why is traveling east worse than west?
- Flying east shortens your day and asks your body clock to fall asleep earlier than usual, which most people find harder. Flying west lengthens your day and asks you to stay up later, which is generally easier to adapt to.
- How do I get over jet lag faster?
- General tips: gradually shift your sleep schedule before you travel, stay hydrated, get well-timed light exposure, keep naps short, and align meals and sleep with local time on arrival. These are informational suggestions, not medical advice.
- Does light exposure help with jet lag?
- Light is the strongest cue for the body clock. In general, after eastward travel many people seek bright morning light and avoid late-evening light; after westward travel, evening light can help. The best timing depends on how far you traveled.
- How many days per time zone to adjust?
- A common estimate is about one day per time zone when traveling east, and slightly faster when traveling west. This calculator uses about one day per zone eastward and roughly 0.8 days per zone westward.
- Is this medical advice?
- No. This tool gives general, informational estimates and tips about jet lag and is not medical advice. If you have a sleep disorder or health condition, talk to a qualified healthcare professional.