Jet Lag Calculator
Pick where you leave from and where you land to see the clock difference, the local time you arrive and a rough guide to how many days your body clock may need to adjust.
Your numbers
How we calculate it
The clock difference is the destination UTC offset minus the offset where you start. Your local arrival time is the departure time plus the flight time plus that difference, and the calculator tells you if that lands on the next or previous day.
Body-clock shift is how far your internal clock must move. Flying east you need to move it earlier, flying west later. In automatic mode the calculator uses whichever direction is the smaller shift, which is how most people think of a trip. You can force a direction if you prefer.
The adjustment estimate uses a common rule of thumb: about one day per hour of shift when flying east, and about one day per 1.5 hours when flying west. People vary a great deal, so treat it as a rough guide, not a prediction.
Assumptions and limits
- UTC offsets do not change for daylight saving time on their own. If a place observes it on your travel date, pick the offset that applies on that date, for example UTC−4 for New York in summer.
- Not medical advice. Age, sleep, light exposure and how you travel all affect jet lag. Ask a clinician if you have a health condition or take time-sensitive medication.
- Flight time should include any layovers if you want the final arrival time.
Frequently asked questions
Is jet lag worse flying east or west?
Most people find eastbound travel harder. It asks your body to fall asleep earlier than it wants to, which is usually harder than staying up later.
How can I reduce jet lag?
Common advice includes moving your sleep time a little toward the destination before you leave, getting daylight at the right times once you arrive and staying hydrated. For personal advice, ask a health professional.
Why does this ask for UTC offsets instead of cities?
Offsets are exact and never ambiguous. Look up your city’s current UTC offset and pick the closest match from the list.
Related calculators
- Hours Between Two Times CalculatorEnter a start time and an end time to get the elapsed hours and minutes, even when the shift crosses midnight.
- Days Between Dates CalculatorPick two dates to see exactly how many days apart they are, along with the same gap in weeks, in years-months-days and in working weekdays.
- Add Days to a Date CalculatorStart with a date and add or subtract any number of days, weeks, months or years to find the resulting date.
- Age CalculatorEnter a date of birth to see your exact age and how many days until your next birthday.
Worked example (a fixed example using the starting numbers, it does not change as you type)
Inputs: Leaving from (UTC offset) = UTC−5 New York; Flying to (UTC offset) = UTC±0 London; Departure time (local) = 21:00; Flight time (hours) = 7; Travel direction = Shorter shift (automatic).
- Clock difference 5 hours ahead
- Local arrival time 09:00 (next day)
- Body-clock shift 5 hours, eastbound (earlier)
- Rough adjustment time about 5 days
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