Jet Lag Calculator: Plan Your Sleep Across Time Zones
Jet lag happens when your body clock is out of step with your destination’s time. A jet lag calculator helps you plan how to shift your sleep before and after a trip. This guide gives the main rules of thumb.
Key takeaways
- Many people adjust at roughly one day per time zone crossed, and travelling east is usually harder.
- Shifting your schedule by an hour a day before departure can reduce the shock.
- Light timing is the main tool for moving your body clock.
- Use the jet lag calculator to plan the shift.
Why jet lag happens
Your circadian rhythm keeps running on home time after you land. Flying east asks you to fall asleep earlier than your body wants, which is usually harder than staying up later when flying west.
Rule-of-thumb adjustment time
| Time zones crossed | Typical adjustment (approximate) |
|---|---|
| 1 to 2 | A day or two |
| 3 to 5 | Roughly 3 to 5 days |
| 6 or more | Up to a week or longer, especially going east |
These are general estimates. Individual responses vary.
Before you fly
If you can, shift your bedtime and wake-up time by about an hour a day in the direction of your destination for a few days. Going east, move earlier. Going west, move later.
After you land
- Switch to local time immediately for meals and bedtime.
- Get daylight at the right time: morning light helps after eastward travel, and afternoon or evening light helps after westward travel.
- Keep naps short, under 30 minutes, early in the day.
- Limit alcohol and late caffeine.
Melatonin is sometimes used for timing shifts, but speak to a doctor or pharmacist first. See our melatonin guide and the general jet lag guide.
Frequently asked questions
Why is flying east worse?
Most people’s internal clocks run slightly longer than 24 hours, so delaying sleep is easier than advancing it.
Should I nap after a long flight?
A short nap early in the day is fine, but long or late naps can slow adjustment.
Sources and further reading: American Academy of Sleep Medicine (aasm.org), Sleep Research Society, National Sleep Foundation (sleepfoundation.org), CDC sleep resources (cdc.gov/sleep). See our full source list and editorial policy. This guide is general information, not medical advice.